# 1989 20 HP Johnson power upgraded to 25 HP for zero dollars



## Stefan

My outboard is a 20 HP Johnson, 1989, 2 Stroke, Model # CJ20CRCEM

I did some research and found out that the 20 HP models from that vintage carry the same powerhead and gear casing as the 25, 30 and 35 HP. 

Difference between the 20 HP and 30 / 35 HP are larger intake manifold and carbs.

Difference between the 20 HP and 25 HP is the intake manifold isn't restricted on the 25 HP. In other words, the 20 HP is the exact same engine as the 25 HP, including the carb and intake manifold, it's just that the intake manifold is restricted on the 20 HP.

I double checked this on BRP's (Bombardier who took over Johnson / Evinrude) website. By using the parts diagrams for the different sized engines I was able to verify this. 

By boring out the intake manifold on my 20 HP motor, to match exactly to the opening of the carb, I gained an extra 5 HP for no funds spent. 

How did I do this? 

First thing I did is carefully remove the intake manifold and carb, which is pretty easy to do. Just take your time. Next, I found a bottle cap that matched the opening of the carb exactly (a peroxide bottle cap with a diameter of 1.25 inches). I then seated the carb onto the intake manifold exactly how it would seat if mounted on the engine, by lining up the bolt holes, and then I sprayed some white lithium grease through the carb opening which provided for an outline over the restrictor plate. 

This gave me a reference point with which to place the peroxide bottle cap on the exposed intake manifold with the carb removed, allowing me to outline with a pencil the exact area on the intake manifold that needed to be bored out in order to allow unrestriced airflow. Next, I used a very small file to carefully file away to the edge of the pencil mark, filing in even strokes. This was a slow process. To clean up the edges I used a dremel tool in order to smooth out the new opening. It is very important at this point to use compressed air, a rag, or whatever thorough method to remove from the intake manifold any steel shillings from filing to ensure that they do not enter the cylinders. This is also a great opportunity to clean up your intake manifold, paint it, and give your carb a good wipe down / cleaning. Finally, I reinstalled the parts.

Results:

Before - with the restricted intake manifold my boat was bogged down, did not plane and topped out around 25 km/h. Even worst with a passenger. I tried shifting weight around, reducing weight on the boat and many other makeshifts solution to get the boat to plane and cruise better. 

After - with the intake manifold now unrestricted my boat planes with ease and cruises along at about 43 km / h. Planes with a passenger and cruises along just a tad slower with the added weight. Increased air flow made my engine easier to start and it now idles better too. Next will be to get a prop with a bigger pitch to squeeze even more speed, as the extra power will be able to turn a higher pitch. I could not be happier with the results, and the best part is it was done for zero dollars expended, only about 2 hours of my time. I get to my fishing destination faster, which means I save fuel because the engine isn't running as much and it is pushing a boat that is on plane rather than bogged down. I tested this for the first time this past week and I am still grining ear to ear. 

Other Considerations - I had originally intended to upgrade my engine by purchasing a 30 hp carb and intake manifold, which would have cost at least $200 if I could find good, used parts. However, by discovering that the intake manifold could be bored open I did not have to go the route of purchasing new hardware, while still achieving the desired result. This mod gave me just the extra power I required. If you have a 20 HP motor of this vintage, why not do the mod, even if you don't need the extra power? If you do need the extra power, this mod might achieve the same result for you as it did for me depending on the size of your boat.

Hope this helped. Good luck, happy boating and fishing.


----------



## Pappy

Great job. I like it when folks actually take the time and do the research to get answers instead of relying on others to do it for them!


----------



## jasper60103

Great job on the motor, and I also liked the boat mod too. Thanks for sharing.
-jasper


----------



## Stefan

Thank you , I couldn't be more happy in my fishing machine. A few small details to finish off, hopefully over the winter time.


----------



## DrNip

Can't beat this! Nice job.


----------



## Plasticmotif

I opened up my carb today and peeked inside...It looks just like this in a 1990 Evinrude 20 CRESB motor. 

I've been planning on trying to find a 30 carb/intake but they aren't that common on e-bay. 

I may just try this. 

Do you have any pictures of actually removing the starter/carb? I can't see an easy way to get the carb off.


----------



## Stefan

[url=https://www.tinboats.net/forum/viewtopic.php?p=327071#p327071 said:


> Plasticmotif » 23 minutes ago[/url]"]I opened up my carb today and peeked inside...It looks just like this in a 1990 Evinrude 20 CRESB motor.
> 
> I've been planning on trying to find a 30 carb/intake but they aren't that common on e-bay.
> 
> I may just try this.
> 
> Do you have any pictures of actually removing the starter/carb? I can't see an easy way to get the carb off.




I don't have any pics of the removal process and I didn't have to remove a starter since my motor is not electric start... However, it was real easy to remove the carb.

There were three components that have to be removed. 

1 The linkage arm (about 1 inch long) that is the go between from the throttle control to the carb regulating the butterfly inside the carb , simply pops off on both ends with steady, light pressure.

2 Two fuel lines, use a small flat head screw driver to pop them off with light pressure

3 Two nuts that secure the carb to the intake manifold. As you loossen the nuts lift the carb at the same time with your other hand so the nuts dont hurt the components that are directly above them. 


The intake manifold is a piece of cake to remove. Just a couple of flat head bolts, the rest i believe were 3/8 inch rachet style bolts, about 5 of them. 

If you're still having problems post some pics of your carb on this thread and we can go from there. Ask any questions you may have. If you end up doing this mod, please let me know how it worked out for you, I'm very interested.


----------



## Plasticmotif

Got my manifold off. Going to start the slow process of rounding out the keyhole!

Starting coarse then using a chainsaw sharpener to buff it out.


----------



## Stefan

[url=https://www.tinboats.net/forum/viewtopic.php?p=327619#p327619 said:


> Plasticmotif » 25 minutes ago[/url]"]Got my manifold off. Going to start the slow process of rounding out the keyhole!
> 
> Starting coarse then using a chainsaw sharpener to buff it out.




That's great! Looking forward to hearing about the results plus any suggestions you might be able to offer that would make this process easier.


----------



## Plasticmotif

Got it roughed in. It's not an exact perfect circle but it's lined up properly. I aligned the carb onto the manifold and stuck a pencil through the butterfly and marked the edges of the carb. I got a 10" rounded file and roughed it in. Polished a bit with a dremel. Now I'm polishing with fine sand paper. Will clean-up and try to install tomorrow!


----------



## Stefan

That's great, the hardest part is over now... I'm sure you did a very good job.

When do you think you're doing to test it out? When you do bring a GPS with you so you can track your speed. 

How is your prop looking? Mine had some burs on it and I used an angle grinder to debur it. Seemed to help quite a bit, will tide me over till I get a new one. The prop on my motor is a 10.5 x 11.. Thinking of trying a higher pitch, but still need to research this a bit more.


----------



## Plasticmotif

Mine's a 10x13.

I'd test it out soon.....but, my registration lapsed. I've not registered the boat to me as I've only had it a short time. So, I've got to pay taxes on it as well. Need to wait till next payday. Had to pay for my wife's last semester of graduate school and car insurance so I was skinned!

If I can get it registered Friday, I'll probably take it out this weekend. Provided I don't go dove hunting.

Speed doesn't matter much to me - as long as it planes out. I wasn't able to plane out with two people in the boat before.


----------



## Stefan

I understand Mac, things are pretty tight, for pretty much everyone it seems... Thank goodness we have our boats to escape for a while... 

I think this mod should help your boat to plane. I wonder if one of those Dol-Fins, might help as well. Ive heard mixed reviews on them, but ive heard instances of them working... I might just try it..


----------



## shawnfish

im a little confused here. you say the difference in the 20hp and 25hp is that the 25 intake is not restricted and the 20 intake is restricted. so in theory the only thing that gives the 25hp 5 more HP than the 20hp is more air into the intake manifold. so you would think that both the 20hp and 25hp have the same carbs but the 20hp intake restricts more air going into the engine hence 5 less HP. but the 20 and 25 have different carbs so I would think that even if both intakes were not restricted it wouldn't matter because the 25 has a bigger carb than the 20hp and would still be putting more air than the 20hp with the intakes being unrestricted so I don't see where the 5 extra hp is coming from with both motors having different carbs and intakes. from the late 70's into the 80's both the 25hp and the 35hp had the same powerheads, intakes and inner exhaust tubes. the difference in 10hp is that the 25hp carbs have a restricter inside the carb throat so to get 35hp out of the 25hp you put a 35 carb on the 25hp motor thats why I cant understand where you get 5 more hp without changing your carbs. granted im tired as hell and may be missing something but this thread got my attention because I have a 1980 25hp Johnson and I put the bigger 35 carb on mine for a 10hp gain and your theory about the intakes just don't add up to me. but like I said im nodding off and may be missing something so don't assume im saying your wrong im just saying that I don't get it... so if you can explain it better I really would like to know if im wrong.


----------



## shawnfish

this is driving me nuts thinking about it so I shot johnny25 a message and asked him to read this and see what he thinks. again if im wrong I apologize and am not saying you don't know what your talking about. im sure after some sleep and I can think straight i'll see that I may be mistaken....


----------



## Charger25

Sounds to me like the the intake just restricts air flow Shawnfish. Like the plates they use in NASCAR limiting the HP. If you look at an engine as if it was an air pump, the smoother the flow of air through the intake and the more efficiently you can scavenge the exhaust ,the more HP you can make.


----------



## Stefan

[url=https://www.tinboats.net/forum/viewtopic.php?p=327756#p327756 said:


> shawnfish » Today, 06:15[/url]"]this is driving me nuts thinking about it so I shot johnny25 a message and asked him to read this and see what he thinks. again if im wrong I apologize and am not saying you don't know what your talking about. im sure after some sleep and I can think straight i'll see that I may be mistaken....




Hi Shawnfish,

Check out this link here to BRP for Johnson 1989, 20 HP and 25 HP models.

20 HP Carb is part # 0433193 (this is what is etched on the carb on my 20 HP as well)
25 HP Carb is part # 0432704

So the carbs are definitely different part #'s, but from all the research I have done the only difference between the two engines is that key hole restrictor plate on the intake manifold of the 20 HP...

Perhaps the carbs are exactly the same, but were just cataloged in their inventory differently as seperate part #'s for sorting purposes??? Or perhaps they just assign the 25 HP a different part #, so it seems like it is a different part and they can charge more $$$ for it? Or maybe I am completely wrong, you could be right and they are different carbs all together?

Either way, the results speak for themselves: when I bored out that key hole on the intake to match the carb perfectly, air flow increased, speed increased, the boat planed, the engine idles better and I'm still smiling. More air resulted in more power...


----------



## shawnfish

[url=https://www.tinboats.net/forum/viewtopic.php?p=327765#p327765 said:


> Stefan » Today, 07:23[/url]"]
> 
> 
> [url=https://www.tinboats.net/forum/viewtopic.php?p=327756#p327756 said:
> 
> 
> 
> shawnfish » Today, 06:15[/url]"]this is driving me nuts thinking about it so I shot johnny25 a message and asked him to read this and see what he thinks. again if im wrong I apologize and am not saying you don't know what your talking about. im sure after some sleep and I can think straight i'll see that I may be mistaken....
> 
> 
> 
> 
> 
> Hi Shawnfish,
> 
> Check out this link here to BRP for Johnson 1989, 20 HP and 25 HP models.
> 
> 20 HP Carb is part # 0433193 (this is what is etched on the carb on my 20 HP as well)
> 25 HP Carb is part # 0432704
> 
> So the carbs are definitely different part #'s, but from all the research I have done the only difference between the two engines is that key hole restrictor plate on the intake manifold of the 20 HP...
> 
> Perhaps the carbs are exactly the same, but were just cataloged in their inventory differently as seperate part #'s for sorting purposes??? Or perhaps they just assign the 25 HP a different part #, so it seems like it is a different part and they can charge more $$$ for it? Or maybe I am completely wrong, you could be right and they are different carbs all together?
> 
> Either way, the results speak for themselves: when I bored out that key hole on the intake to match the carb perfectly, air flow increased, speed increased, the boat planed, the engine idles better and I'm still smiling. More air resulted in more power...
Click to expand...



I checked 2 other sites along with BPR before I posted to be sure. and if the carbs are the same but have different numbers for the 20's and 25's then you would think the intakes would be assigned different numbers?????? to me it just seems logical that the 25 is capable of pushing more air than the 20 because why else wouldn't both motors have the same carbs with the difference being the restrictor on the intake on the 20hp? I guess im torturing myself thinking about it because if you say you got more hp from doing it then that's all that really matters I just dont get it lol! that's weird your casting numbers show up as the actual part number for your carb because I know up until at least 1984 if you run any casting number in a parts search 98% of the time it comes up as there is no match for that number and I do know that some parts from back then had the same cast numbers on them but the parts would be used on different years and hp's motors.... and to charger that's exactly how I was thinking in regards to the restrictor plate races for nascar......


----------



## Johny25

Ok I skimmed the thread real quick as I am in a hurry today but will try and give my 2 cents. Yes the only difference in 20 and 25hp in this year is the restricted intake design. The 20 and 25hp starting in 1985 had identical carburetors. I believe I covered this in my 20/25hp to 30hp conversion thread but maybe I didn't? We could debate all day whether it actually gives an extra 5hp by boring the intake out but unless someone has a dyno for outboards we may never know. the theory is there though.....more air in should make more HP. I will also say that I owned an 85' 20hp and it did not seem to run as smooth as my 85' 30hp or my 88' 25hp and this I suspect was because of the restricted intake. The motor really seemed to want more air.

Now a little history on the 20hp.......the 20hp motors that we are talking about came out in 1985. The same year OMC started prop rating the HP of there motors. Before that the 20hp was last made in 73' in the smaller 22ci block, and only the johnson logo or tag was released in the 20hp. Evinrude never had the 20hp tag until 1985....they were labeled 18hp pre 74' I believe although I suspect motors were identical. Likely a marketing ploy of some sort. Also in 1984 the 35hp was discontinued and became the 30hp of 1985. The 35 was brought back for one year in 1987 but it was a restricted 40/50 HP motor. And then again somewhere in the 90's I believe it came back but now I am at the limits of my memory without researching again.

But in short......in 1985 the 20hp came out and had a restricted intake, and only that is what separated it from the 25 for several years. I'm not sure but I believe at some point there was more than just the intake difference in the 20 and 25 but cannot remember when it was? In the 90's I believe


----------



## shawnfish

[url=https://www.tinboats.net/forum/viewtopic.php?p=327778#p327778 said:


> Johny25 » 42 minutes ago[/url]"]Ok I skimmed the thread real quick as I am in a hurry today but will try and give my 2 cents. Yes the only difference in 20 and 25hp in this year is the restricted intake design. The 20 and 25hp starting in 1985 had identical carburetors. I believe I covered this in my 20/25hp to 30hp conversion thread but maybe I didn't? We could debate all day whether it actually gives an extra 5hp by boring the intake out but unless someone has a dyno for outboards we may never know. the theory is there though.....more air in should make more HP. I will also say that I owned an 85' 20hp and it did not seem to run as smooth as my 85' 30hp or my 88' 25hp and this I suspect was because of the restricted intake. The motor really seemed to want more air.
> 
> Now a little history on the 20hp.......the 20hp motors that we are talking about came out in 1985. The same year OMC started prop rating the HP of there motors. Before that the 20hp was last made in 73' in the smaller 22ci block, and only the johnson logo or tag was released in the 20hp. Evinrude never had the 20hp tag until 1985....they were labeled 18hp pre 74' I believe although I suspect motors were identical. Likely a marketing ploy of some sort. Also in 1984 the 35hp was discontinued and became the 30hp of 1985. The 35 was brought back for one year in 1987 but it was a restricted 40/50 HP motor. And then again somewhere in the 90's I believe it came back but now I am at the limits of my memory without researching again.
> 
> But in short......in 1985 the 20hp came out and had a restricted intake, and only that is what separated it from the 25 for several years. I'm not sure but I believe at some point there was more than just the intake difference in the 20 and 25 but cannot remember when it was? In the 90's I believe




ok so starting in 85 the 20 and 25 had identical carburetors but for some reason or another they used different part numbers on the carbs and its the restricted intake on the 20 that makes the difference and not carb size.. hmmmmm....... well that makes sense to me, logical sense? no. but I understand now why my 1980 25 carb is the same exact size as the 35 carb and both have different numbers with the only difference being the 25 has a plastic ring inside the throat narrowing it to restrict the air flow a bit and to make the same powerhead as the 35 only produce 25hp. well Stefan sorry I drug this out and johnny25 into it to help me understand how and why but my hats off to ya for using your melon and getting 5 more HP out of your motor without spending a dime or whatever you use up there for coin. and thanks a lot johnny25 for going out of your way once again and helping a fella out!!!!


----------



## Stefan

[/quote]ok so starting in 85 the 20 and 25 had identical carburetors but for some reason or another they used different part numbers on the carbs and its the restricted intake on the 20 that makes the difference and not carb size.. hmmmmm....... well that makes sense to me, logical sense? no. but I understand now why my 1980 25 carb is the same exact size as the 35 carb and both have different numbers with the only difference being the 25 has a plastic ring inside the throat narrowing it to restrict the air flow a bit and to make the same powerhead as the 35 only produce 25hp. well Stefan sorry I drug this out and johnny25 into it to help me understand how and why but my hats off to ya for using your melon and getting 5 more HP out of your motor without spending a dime or whatever you use up there for coin. and thanks a lot johnny25 for going out of your way once again and helping a fella out!!!![/quote]

Shawnfish, this great info I am glad that we all looked into it... It does seem weird that OMC would restrict the motor like this. I mean why build a 20 HP motor when it is exactly the same as the 25 HP? Why not just offer a 25 HP? 

I guess it's economies of scale, building motors with the same main components, but very subtle differences... Like car companies build vehicles on identical platforms to lower costs? Also, this way they can offer a wider range of motors to the consumer?? 

The extra power as a result of the mod is great.


----------



## Johny25

Well in 1985 the 20 and 25 had the exact same carb and part number 0395279 and the 20 and 25hp carried exact carb numbers up to 1988 at least. And I believe it continued after that it just becomes harder to trace the numbers.

All motor manufacturers use a single block casting to produce a couple or several different horse power ratings. This is for many reasons including cost and profit to the manufacturer, more HP options for consumer to get largest HP motor for their boat without going over CG transom tag regulations, and also fuel economy. It is the same with the 9.9hp that was made for so many years, all it was really is a de-tuned 15hp. And believe me there is a pretty noticeable increase in hours per gallon that your motor will burn by making HP modifications. I have done the 9.9 to 15hp conversion and the 25 to 30hp conversion and very easily could tell I was eating more fuel. But that is the price you pay for more ponies  

Believe it or not some people don't care how fast their boat goes, just that it gets on plane and the fuel economy is good #-o and then there is the rest of us that think everything should and could go a little faster :mrgreen:


----------



## Stefan

[url=https://www.tinboats.net/forum/viewtopic.php?p=327794#p327794 said:


> Johny25 » Today, 13:51[/url]"]Well in 1985 the 20 and 25 had the exact same carb and part number 0395279 and the 20 and 25hp carried exact carb numbers up to 1988 at least. And I believe it continued after that it just becomes harder to trace the numbers.
> 
> All motor manufacturers use a single block casting to produce a couple or several different horse power ratings. This is for many reasons including cost and profit to the manufacturer, more HP options for consumer to get largest HP motor for their boat without going over CG transom tag regulations, and also fuel economy. It is the same with the 9.9hp that was made for so many years, all it was really is a de-tuned 15hp. And believe me there is a pretty noticeable increase in hours per gallon that your motor will burn by making HP modifications. I have done the 9.9 to 15hp conversion and the 25 to 30hp conversion and very easily could tell I was eating more fuel. But that is the price you pay for more ponies
> 
> Believe it or not some people don't care how fast their boat goes, just that it gets on plane and the fuel economy is good #-o and then there is the rest of us that think everything should and could go a little faster :mrgreen:



Some really great points. I think that the mod will save me fuel because now the boat planes, so the motor isn't working as hard to pushit along, plus it's not operating as much because I get to my destinations faster. For trolling I use a 6 HP evinrude as a kicker, which saves me a ton of fuel...


----------



## Johny25

Likely your motor was not running the correct recommended RPM if it wasn't getting your boat on plane. Being that you just bored the intake your fuel consumption should be better being you can plane now. I say get the intake and 30hp carb and go faster 8) 

I made a post a couple years ago trying to justify that I was saving fuel by going faster. My theory was I got to my fishing spot faster and my motor was running for less time, hence the less fuel I burned :lol: Well I was wrong #-o I burned way more fuel cause I would go more places in a day and ran the motor more often so it really didn't save on anything


----------



## Stefan

[url=https://www.tinboats.net/forum/viewtopic.php?p=327818#p327818 said:


> Johny25 » 41 minutes ago[/url]"]Likely your motor was not running the correct recommended RPM if it wasn't getting your boat on plane. Being that you just bored the intake your fuel consumption should be better being you can plane now. I say get the intake and 30hp carb and go faster 8)
> 
> I made a post a couple years ago trying to justify that I was saving fuel by going faster. My theory was I got to my fishing spot faster and my motor was running for less time, hence the less fuel I burned :lol: Well I was wrong #-o I burned way more fuel cause I would go more places in a day and ran the motor more often so it really didn't save on anything



LOL for real, that is too funny. The first weekend I had it out with the mod, I found myself booting around just for the sake of booting around because I was so happy the motor was working so well. I think you're right, I'll end up using more fuel now because I can... That being said, I agree with the notion of getting the 30 HP carb and intake. I can only imagine how fast the fishing machine would go with those parts, plus my 6 hp started and full throttle at the same time!

Thanks so much for all of your input on this threat and the knowledge you've shared on other threads. I've read through your mod extensively.


----------



## shawnfish

Johny25 said:


> Likely your motor was not running the correct recommended RPM if it wasn't getting your boat on plane. Being that you just bored the intake your fuel consumption should be better being you can plane now. I say get the intake and 30hp carb and go faster 8)
> 
> I made a post a couple years ago trying to justify that I was saving fuel by going faster. My theory was I got to my fishing spot faster and my motor was running for less time, hence the less fuel I burned :lol: Well I was wrong #-o I burned way more fuel cause I would go more places in a day and ran the motor more often so it really didn't save on anything





when I first read Stefan's post the first time prop change came to mind but kept reading and he had already tore his motor apart and got after it. and im with the I wanna be going down the lake with my hair on fire crowd and if I have to spend a little more on fuel really its not that big of a deal because 90% of the fishing I do is on lakes no bigger than 200 or so acres. I love these threads like yours and johnny25's especially because they are done on old OMC's and im sure you guys have seen my posts about the OMC small outboards (40hp and under) being the best built most reliable and user friendly outboards ever built and I would put them up against any brand new outboard on the market today id also bet that our pre 90's johnny/rudes will still be running after the ones being built today are in the scrap heap as long as they have just the very basic maintenance stuff kept up on them. I also believe what ive heard from some mechanics and a couple very knowledgeable guys right here on this site that from the late 50's until the 90's that these motors were over engineered and it makes sense because theres more older OMC's still making wakes than there are all of the other older OB's combined. that's all my grandpa would buy was OMC and my 1980 was the last brand new OB he bought and I inherited it so to speak and for almost 34 yrs old that motor has never left me in the breach besides when the operator might have forgot to put fuel in it once or twice lol! so yeah I like OMC's and defend them like they are my little sister surrounded by teenage boys!


----------



## Stefan

Shawnfish, you are absolutely right, I think that the OMC engines from the 70's and 80's are over engineered. I spoke to a guy who worked at the OMC factory where my engine was made, just east of where i live in Peterborough Canada, and he told me that the engines are rock solid. These things are tanks, they go and go and go with just regular maintenance. 

I have a 1989 Johnson 20 HP, 1972 Johnson 20 HP (anniversary edition) I scored on a trade for an old tattered portable ice hut I didn't use anymore and a 1973 6 HP Evinrude Fisherman. All amazing engines that run great. 

The only issue I worry about is ethanol killing the seals and lines, but I treat the gas with stabilizer, so apparently this is supposed to help. This winter I hope to rebuild the carbs on all three engines and if you guys don't mind I might be drawing on you for some help if I encounter problems. Also hoping to clean up the engines, paint them up and order decal kits for all of them...


----------



## Plasticmotif

I had it reinstalled running after boring the intake.. I had a small leak from the float nipple. Tightened it up and it broke right off. Doh!

So, it's apart again today. I got the broken nipple out. New ones at my marine shop. Pick it up tomorrow. 

Well see how it goes after that!


----------



## shawnfish

[url=https://www.tinboats.net/forum/viewtopic.php?p=327778#p327778 said:


> Johny25 » Today, 10:28[/url]"]Ok I skimmed the thread real quick as I am in a hurry today but will try and give my 2 cents. Yes the only difference in 20 and 25hp in this year is the restricted intake design. The 20 and 25hp starting in 1985 had identical carburetors. I believe I covered this in my 20/25hp to 30hp conversion thread but maybe I didn't? We could debate all day whether it actually gives an extra 5hp by boring the intake out but unless someone has a dyno for outboards we may never know. the theory is there though.....more air in should make more HP. I will also say that I owned an 85' 20hp and it did not seem to run as smooth as my 85' 30hp or my 88' 25hp and this I suspect was because of the restricted intake. The motor really seemed to want more air.
> 
> Now a little history on the 20hp.......the 20hp motors that we are talking about came out in 1985. The same year OMC started prop rating the HP of there motors. Before that the 20hp was last made in 73' in the smaller 22ci block, and only the johnson logo or tag was released in the 20hp. Evinrude never had the 20hp tag until 1985....they were labeled 18hp pre 74' I believe although I suspect motors were identical. Likely a marketing ploy of some sort. Also in 1984 the 35hp was discontinued and became the 30hp of 1985. The 35 was brought back for one year in 1987 but it was a restricted 40/50 HP motor. And then again somewhere in the 90's I believe it came back but now I am at the limits of my memory without researching again.
> 
> But in short......in 1985 the 20hp came out and had a restricted intake, and only that is what separated it from the 25 for several years. I'm not sure but I believe at some point there was more than just the intake difference in the 20 and 25 but cannot remember when it was? In the 90's I believe



they brought back the 35hp in 96 but it was a 3cyl not a 2cyl and was still in production in 2002 and maybe longer but I didn't want to read anymore tonight because im tired. they also made a 35hp jet from 93-97 and they made a 20hp in 97 for one year but like I said I made it to 2002 and wanted to post this before I crash for the night... I have a awesome site packed full of info for outboards, stern drives etc... if anyone would like it....


----------



## Stefan

[url=https://www.tinboats.net/forum/viewtopic.php?p=327846#p327846 said:


> Plasticmotif » Today, 21:26[/url]"]I had it reinstalled running after boring the intake.. I had a small leak from the float nipple. Tightened it up and it broke right off. Doh!
> 
> So, it's apart again today. I got the broken nipple out. New ones at my marine shop. Pick it up tomorrow.
> 
> Well see how it goes after that!




Let us know the results Mac, I am really looking forward to reading if it makes a big difference on your boat...


----------



## Stefan

they brought back the 35hp in 96 but it was a 3cyl not a 2cyl and was still in production in 2002 and maybe longer but I didn't want to read anymore tonight because im tired. they also made a 35hp jet from 93-97 and they made a 20hp in 97 for one year but like I said I made it to 2002 and wanted to post this before I crash for the night... I have a awesome site packed full of info for outboards, stern drives etc... if anyone would like it....[/quote]


that would be great Shawnfish, could you post the link?


----------



## shawnfish

im computer challenged so I will just type it in https://boatinfo.no/lib/library.html

manuals, brochures and other technical documents from the last 100yrs. I think I got it off this site but cant remember.

rebuilding your carbs is probably a lot easier than you think if you have not done it before and like you said theres help here. you wont find factory decals that are still available for your motors except maybe the 90 at least not down here south of the border. theres a guy who makes the best factory reproduction decal sets that ive ever seen and actually I couldn't tell they were not factory and are hands over fists better than the ones on ebay and other sites in regards to color match and quality material and if you want he will make you the factory decals with different colors if that's what you want or have them modified a certain way if you wanna go that route almost every set ive seen on the site run 75.00 to 110.00 dollars for our HP size anyways its NY.MARINE and since your up in Canada I have a couple questions for you. what does the Canada derated in your model number mean? and also I was doing my daily screen shopping on ebay and saw a Johnson cowling that said TNT on it with like a yellowish horizontal stripe that looks factory to me and in the description for the seller it said "from Canada" have you seen one like this up there


----------



## Charger25

This whole thread is a prime example of why I love this site. Useful exchange of Ideas, information, opinions and knowledge. 
I humbly appalled you all. =D> =D> =D> And thanks for the boatinfo link shawnfish.


----------



## Stefan

[url=https://www.tinboats.net/forum/viewtopic.php?p=327864#p327864 said:


> shawnfish » Today, 05:38[/url]"]im computer challenged so I will just type it in https://boatinfo.no/lib/library.html
> 
> manuals, brochures and other technical documents from the last 100yrs. I think I got it off this site but cant remember.
> 
> rebuilding your carbs is probably a lot easier than you think if you have not done it before and like you said theres help here. you wont find factory decals that are still available for your motors except maybe the 90 at least not down here south of the border. theres a guy who makes the best factory reproduction decal sets that ive ever seen and actually I couldn't tell they were not factory and are hands over fists better than the ones on ebay and other sites in regards to color match and quality material and if you want he will make you the factory decals with different colors if that's what you want or have them modified a certain way if you wanna go that route almost every set ive seen on the site run 75.00 to 110.00 dollars for our HP size anyways its NY.MARINE and since your up in Canada I have a couple questions for you. what does the Canada derated in your model number mean? and also I was doing my daily screen shopping on ebay and saw a Johnson cowling that said TNT on it with like a yellowish horizontal stripe that looks factory to me and in the description for the seller it said "from Canada" have you seen one like this up there




Shawnfish, that link you posted is a wealth of information, thank you so much! I've booked marked it and will look through that extensively. 

Thanks for the decals source, I've got a great source just north of Toronto that custom prints them as well for a pretty reasonable price. It's amazing what new decals will do for the look of the engine. But regarding your two questions, about Canada de-rated in the model number - I'm not sure what you mean, can you post the model # that you are talking about.... and the TNT emblem on the cowling of the motor; I have never seen this before, so I really don't know to be honest with you.. . but if you post the link for what you saw that might yield some answers...


----------



## Plasticmotif

Got it roughed in. Was backfiring out of the water when in neutral. Hopefully it's just bad gas and no back pressure on the exhaust.

I got it registered today. Will be taking her out tomorrow see if I can get her to plane!


----------



## shawnfish

[url=https://www.tinboats.net/forum/viewtopic.php?p=327889#p327889 said:


> Stefan » Yesterday, 07:48[/url]"]
> 
> 
> [url=https://www.tinboats.net/forum/viewtopic.php?p=327864#p327864 said:
> 
> 
> 
> shawnfish » Today, 05:38[/url]"]im computer challenged so I will just type it in https://boatinfo.no/lib/library.html
> 
> manuals, brochures and other technical documents from the last 100yrs. I think I got it off this site but cant remember.
> 
> rebuilding your carbs is probably a lot easier than you think if you have not done it before and like you said theres help here. you wont find factory decals that are still available for your motors except maybe the 90 at least not down here south of the border. theres a guy who makes the best factory reproduction decal sets that ive ever seen and actually I couldn't tell they were not factory and are hands over fists better than the ones on ebay and other sites in regards to color match and quality material and if you want he will make you the factory decals with different colors if that's what you want or have them modified a certain way if you wanna go that route almost every set ive seen on the site run 75.00 to 110.00 dollars for our HP size anyways its NY.MARINE and since your up in Canada I have a couple questions for you. what does the Canada derated in your model number mean? and also I was doing my daily screen shopping on ebay and saw a Johnson cowling that said TNT on it with like a yellowish horizontal stripe that looks factory to me and in the description for the seller it said "from Canada" have you seen one like this up there
> 
> 
> 
> 
> 
> ok your model number CJ20CRCEM C=CANADA J=Johnson 20=HP CR=CANADA DERATED CE=89 M=PRODUCTION RUN
> 
> 
> not sure if your familiar with the year code designation or model code designation that they started using in 1980 but if your not you can find it at evinrude,brp marineengines... and you use that to decipher the model number for year built and options like long or short shaft, rope or electric start, tiller or remote etc....it has other countries listed as derated too and I wonder if its something to do with their emission standards or something cuz that's all I can think of.....
> Shawnfish, that link you posted is a wealth of information, thank you so much! I've booked marked it and will look through that extensively.
> 
> Thanks for the decals source, I've got a great source just north of Toronto that custom prints them as well for a pretty reasonable price. It's amazing what new decals will do for the look of the engine. But regarding your two questions, about Canada de-rated in the model number - I'm not sure what you mean, can you post the model # that you are talking about.... and the TNT emblem on the cowling of the motor; I have never seen this before, so I really don't know to be honest with you.. . but if you post the link for what you saw that might yield some answers...
Click to expand...


theres a pic of the hood. if I didn't tell you already marineengine.com has NOS factory decals for your motor for 45.00 and if I was you id jump all over that deal, gotta be cheaper than custom printed decals....


----------



## shawnfish

it looks factory to me the way the stripe looks like it goes behind that tag/emblem on the back.....


----------



## longshot

I just did something very similar to this on my 2003 tohatsu. It needed the carb overhauled and I discovered the 9.9/15/18 were all the same except for the carbs. So I ordered a new 18 carb runs great in the tank I will be trying it out at the lake in the morning


----------



## Stefan

[url=https://www.tinboats.net/forum/viewtopic.php?p=327977#p327977 said:


> longshot » Today, 09:55[/url]"]I just did something very similar to this on my 2003 tohatsu. It needed the carb overhauled and I discovered the 9.9/15/18 were all the same except for the carbs. So I ordered a new 18 carb runs great in the tank I will be trying it out at the lake in the morning




How did it go? did you notice a big diference in speed and power??


----------



## Stefan

[url=https://www.tinboats.net/forum/viewtopic.php?p=327955#p327955 said:


> Plasticmotif » Yesterday, 21:19[/url]"]Got it roughed in. Was backfiring out of the water when in neutral. Hopefully it's just bad gas and no back pressure on the exhaust.
> 
> I got it registered today. Will be taking her out tomorrow see if I can get her to plane!




Platcimotif, congrats on getting her registered??? How did it go today? Did you notice differnces? Any suggestions you might be able to offer??

I hope things went awesome!


----------



## Stefan

[url=https://www.tinboats.net/forum/viewtopic.php?p=327975#p327975 said:


> shawnfish » Today, 09:14[/url]"]it looks factory to me the way the stripe looks like it goes behind that tag/emblem on the back.....




I talked to a buddy today and he said that TNT stands for Tilt and Trim! verfied this online at a couple of sources as well... 

https://forums.iboats.com/johnson-evinrude-outboards/how-does-my-power-tilt-trim-thing-work-174330.html


----------



## Stefan

[/quote] theres a pic of the hood. if I didn't tell you already marineengine.com has NOS factory decals for your motor for 45.00 and if I was you id jump all over that deal, gotta be cheaper than custom printed decals....[/quote]

thank you very much for the decal source shawnfish, im checking it out right now... marineengine.com


----------



## NH-PLAY

Ok so my 72 9.9 is really a 15hp just down sized


----------



## Johny25

Nope I am sorry to say that you have a 9.5hp turtleback and not a 9.9hp. In 1972 they made a 9.5hp with the 15ci block and then the next step up was the 20hp in the 22ci block. The 9.9hp 13.2ci blocks did not come out until 74' which is when the 15hp were also put back into production.....before that the 15hp was last made in 1956


----------



## Plasticmotif

Well, with the wife/kiddo and me in the boat it planed out. Definite performance increase! And! I caught a fish in a really over fished lake.

No backfiring issues in the water. I think it needed back pressure on the exhaust. Runs great. Not over-revved at all. My tach isn't in yet. Whenever it gets in, I'll start fooling around with getting a better prop. Mine's in need of replacing.

Lastly, I'll need to play around with my trim when by myself and the idle setting isn't exact but, the boat is doing well. 

I don't know that I could be of any help. 

I think any OMC motor from 1986 to 2005 will work. I think any 20-25 can be turned into a 30. Just have to find the parts.


----------



## Stefan

[url=https://www.tinboats.net/forum/viewtopic.php?p=327998#p327998 said:


> Johny25 » 22 minutes ago[/url]"]Nope I am sorry to say that you have a 9.5hp turtleback and not a 9.9hp. In 1972 they made a 9.5hp with the 15ci block and then the next step up was the 20hp in the 22ci block. The 9.9hp 13.2ci blocks did not come out until 74' which is when the 15hp were also put back into production.....before that the 15hp was last made in 1956



Johny25,

You say in 72 Johnson made a 20 hp in the 22CI block. What do you mean by 22CI? The reason I ask is because I have a 20 HP 72 Johnson, and I'm wondering if there are possiblities for upgrading / moding it to squeeze more performance out of it?


----------



## Stefan

[url=https://www.tinboats.net/forum/viewtopic.php?p=328002#p328002 said:


> Plasticmotif » 21 minutes ago[/url]"]
> 
> 
> 
> 
> 
> Well, with the wife/kiddo and me in the boat it planed out. Definite performance increase! And! I caught a fish in a really over fished lake.
> 
> No backfiring issues in the water. I think it needed back pressure on the exhaust. Runs great. Not over-revved at all. My tach isn't in yet. Whenever it gets in, I'll start fooling around with getting a better prop. Mine's in need of replacing.
> 
> Lastly, I'll need to play around with my trim when by myself and the idle setting isn't exact but, the boat is doing well.
> 
> I don't know that I could be of any help.
> 
> I think any OMC motor from 1986 to 2005 will work. I think any 20-25 can be turned into a 30. Just have to find the parts.



THats fantastic news that you noticed a difference! Congrats, I'm really glad it worked out for you the same as it did for me... And thanks for posting that pic, looks like you and your family had an awesome day on the water! Keep up the great fishing and boating!

Are you going to be revamping your boat?


----------



## shawnfish

[url=https://www.tinboats.net/forum/viewtopic.php?p=328003#p328003 said:


> Stefan » Today, 13:00[/url]"]
> 
> 
> [url=https://www.tinboats.net/forum/viewtopic.php?p=327998#p327998 said:
> 
> 
> 
> Johny25 » 22 minutes ago[/url]"]Nope I am sorry to say that you have a 9.5hp turtleback and not a 9.9hp. In 1972 they made a 9.5hp with the 15ci block and then the next step up was the 20hp in the 22ci block. The 9.9hp 13.2ci blocks did not come out until 74' which is when the 15hp were also put back into production.....before that the 15hp was last made in 1956
> 
> 
> 
> 
> Johny25,
> 
> You say in 72 Johnson made a 20 hp in the 22CI block. What do you mean by 22CI? The reason I ask is because I have a 20 HP 72 Johnson, and I'm wondering if there are possiblities for upgrading / moding it to squeeze more performance out of it?
Click to expand...



HE MEANS YOUR BLOCK IS 22 CUBIC INCHES...


----------



## shawnfish

[url=https://www.tinboats.net/forum/viewtopic.php?p=328003#p328003 said:


> Stefan » Today, 13:00[/url]"]
> 
> 
> [url=https://www.tinboats.net/forum/viewtopic.php?p=327998#p327998 said:
> 
> 
> 
> Johny25 » 22 minutes ago[/url]"]Nope I am sorry to say that you have a 9.5hp turtleback and not a 9.9hp. In 1972 they made a 9.5hp with the 15ci block and then the next step up was the 20hp in the 22ci block. The 9.9hp 13.2ci blocks did not come out until 74' which is when the 15hp were also put back into production.....before that the 15hp was last made in 1956
> 
> 
> 
> 
> Johny25,
> 
> You say in 72 Johnson made a 20 hp in the 22CI block. What do you mean by 22CI? The reason I ask is because I have a 20 HP 72 Johnson, and I'm wondering if there are possiblities for upgrading / moding it to squeeze more performance out of it?
Click to expand...



THE 20 AND 25 IN 72 BOTH HAVE THE SAME POWERHEAD...


----------



## shawnfish

[url=https://www.tinboats.net/forum/viewtopic.php?p=328007#p328007 said:


> shawnfish » 4 minutes ago[/url]"]
> 
> 
> [url=https://www.tinboats.net/forum/viewtopic.php?p=328003#p328003 said:
> 
> 
> 
> Stefan » Today, 13:00[/url]"]
> 
> 
> [url=https://www.tinboats.net/forum/viewtopic.php?p=327998#p327998 said:
> 
> 
> 
> Johny25 » 22 minutes ago[/url]"]Nope I am sorry to say that you have a 9.5hp turtleback and not a 9.9hp. In 1972 they made a 9.5hp with the 15ci block and then the next step up was the 20hp in the 22ci block. The 9.9hp 13.2ci blocks did not come out until 74' which is when the 15hp were also put back into production.....before that the 15hp was last made in 1956
> 
> 
> 
> 
> Johny25,
> 
> You say in 72 Johnson made a 20 hp in the 22CI block. What do you mean by 22CI? The reason I ask is because I have a 20 HP 72 Johnson, and I'm wondering if there are possiblities for upgrading / moding it to squeeze more performance out of it?
> 
> Click to expand...
> 
> 
> 
> THE 20 AND 25 IN 72 BOTH HAVE THE SAME POWERHEAD...
Click to expand...


THEY ALSO HAVE THE SAME INTAKES, CARBS AND EXHAUST TUBES... ALL 4 PART NUMBERS MATCH. NOT SURE WHAT MAKES THEM DIFFERENT MAYBE HIGH SPEED ORFICE??? LOOKS LIKE YOU GOT SOMETHING TO DO.....


----------



## Johny25

Yes the ci stands for cubic inches like shawnfish stated, and I show a different carb number for the 20 and 25hp in 1972 but not sure beyond that. Some investigating may be in order for you possibly.


----------



## shawnfish

[url=https://www.tinboats.net/forum/viewtopic.php?p=328024#p328024 said:


> Johny25 » 29 minutes ago[/url]"]Yes the ci stands for cubic inches like shawnfish stated, and I show a different carb number for the 20 and 25hp in 1972 but not sure beyond that. Some investigating may be in order for you possibly.




where are you looking at the numbers? on evinrudes site it shows the replacement numbers not matching and marineengine shows the original numbers matching.... I tend to believe the originals but yeah I think a bit more investigating is needed...


----------



## Johny25

Marineengine and boats.net shows the 20hp with carb number 384529 and the 25hp as 384530 in 1972 and the only thing I can see from a quick glance that is different is the jets......the 20hp having the 67D and the 25hp having the 72D


----------



## shawnfish

[url=https://www.tinboats.net/forum/viewtopic.php?p=328040#p328040 said:


> Johny25 » Today, 00:33[/url]"]Marineengine and boats.net shows the 20hp with carb number 384529 and the 25hp as 384530 in 1972 and the only thing I can see from a quick glance that is different is the jets......the 20hp having the 67D and the 25hp having the 72D




just looked on ME agagin. 25r72r and 20r72r both have the 0383725 carburetor and the 20hp has the 67D and the 25 the 72D.


----------



## Johny25

I think you are looking at just the carb body part number


----------



## Johny25

Look at the carburetor assembly part number, this would be the entire carburetor with all the parts. If the numbers don't match then you can be assured something is different in the carbs


----------



## shawnfish

[url=https://www.tinboats.net/forum/viewtopic.php?p=328062#p328062 said:


> Johny25 » Today, 09:58[/url]"]Look at the carburetor assembly part number, this would be the entire carburetor with all the parts. If the numbers don't match then you can be assured something is different in the carbs




correct. lol! I don't know why I did that I know better. may have had 1 or 5 too many brew ha's yesterday :beer:


----------



## Johny25

:beer: nothing wrong with that


----------



## Stefan

[url=https://www.tinboats.net/forum/viewtopic.php?p=328042#p328042 said:


> shawnfish » Today, 02:46[/url]"]
> 
> 
> [url=https://www.tinboats.net/forum/viewtopic.php?p=328040#p328040 said:
> 
> 
> 
> Johny25 » Today, 00:33[/url]"]Marineengine and boats.net shows the 20hp with carb number 384529 and the 25hp as 384530 in 1972 and the only thing I can see from a quick glance that is different is the jets......the 20hp having the 67D and the 25hp having the 72D
> 
> 
> 
> 
> 
> just looked on ME agagin. 25r72r and 20r72r both have the 0383725 carburetor and the 20hp has the 67D and the 25 the 72D.
Click to expand...



Ii am going to investigate this further, with all the information posted thus far on the 72 johnson 20 HP as a potential upgrade looks promising. 

Once I end up doing the mod, I will post pics and start a similar thread for this model engine. I just have to buy some parts for this engine, as it is missing a couple of minor parts, like the lean / rich linkage arm. She needs just a bit of attention. Once I get her upto snuff I'll start in on the mod and go from there... 

These engines are so versaitile and intuitive, with due care and research it is very easy to work on them


----------



## longshot

[url=https://www.tinboats.net/forum/viewtopic.php?p=327991#p327991 said:


> Stefan » 31 Aug 2013, 14:01[/url]"]
> 
> 
> [url=https://www.tinboats.net/forum/viewtopic.php?p=327977#p327977 said:
> 
> 
> 
> longshot » Today, 09:55[/url]"]I just did something very similar to this on my 2003 tohatsu. It needed the carb overhauled and I discovered the 9.9/15/18 were all the same except for the carbs. So I ordered a new 18 carb runs great in the tank I will be trying it out at the lake in the morning
> 
> 
> 
> 
> 
> How did it go? did you notice a big diference in speed and power??
Click to expand...

 
I took it to the lake today and ran it hard. Burned up about 5 gallons of gas. We had a cooler two bags of gear tackle boxes live well full trolling motor and battery and full fuel tank. We were able to obtain 21 mph on the gps and it was very rough out. Before I changed carb and raised jack plate all I could get was 16 mph plus it started on the first pull every time. My boat is a G3 1544


----------



## Stefan

[url=https://www.tinboats.net/forum/viewtopic.php?p=328119#p328119 said:


> longshot » 13 minutes ago[/url]"]
> 
> 
> [url=https://www.tinboats.net/forum/viewtopic.php?p=327991#p327991 said:
> 
> 
> 
> Stefan » 31 Aug 2013, 14:01[/url]"]
> 
> 
> [url=https://www.tinboats.net/forum/viewtopic.php?p=327977#p327977 said:
> 
> 
> 
> longshot » Today, 09:55[/url]"]I just did something very similar to this on my 2003 tohatsu. It needed the carb overhauled and I discovered the 9.9/15/18 were all the same except for the carbs. So I ordered a new 18 carb runs great in the tank I will be trying it out at the lake in the morning
> 
> 
> 
> 
> 
> How did it go? did you notice a big diference in speed and power??
> 
> Click to expand...
> 
> 
> I took it to the lake today and ran it hard. Burned up about 5 gallons of gas. We had a cooler two bags of gear tackle boxes live well full trolling motor and battery and full fuel tank. We were able to obtain 21 mph on the gps and it was very rough out. Before I changed carb and raised jack plate all I could get was 16 mph plus it started on the first pull every time. My boat is a G3 1544
Click to expand...


That is pretty great improvement - 33% on speed! And probably a whole lot less frustration with the boat planing quicker I bet... Although the fuel consumption would be higher, who gives a damn when you're having that much fun! wooohoooo


----------



## longshot

We made a 45 min WOT run across the lake and then 45 min back and it was really rough. Probably could have gotten a little more speed if we were not jumping boat wakes and wind blown waves the whole way. My wife wants to kill me


----------



## Stefan

[url=https://www.tinboats.net/forum/viewtopic.php?p=328125#p328125 said:


> longshot » 11 minutes ago[/url]"]We made a 45 min WOT run across the lake and then 45 min back and it was really rough. Probably could have gotten a little more speed if we were not jumping boat wakes and wind blown waves the whole way. My wife wants to kill me



haha that's awesome! well one benefit with the extra speed is that you can get out of rough water situations faster, or conversely, enjoy them that much more!


----------



## shawnfish

[url=https://www.tinboats.net/forum/viewtopic.php?p=328126#p328126 said:


> Stefan » Today, 20:23[/url]"]
> 
> 
> [url=https://www.tinboats.net/forum/viewtopic.php?p=328125#p328125 said:
> 
> 
> 
> longshot » 11 minutes ago[/url]"]We made a 45 min WOT run across the lake and then 45 min back and it was really rough. Probably could have gotten a little more speed if we were not jumping boat wakes and wind blown waves the whole way. My wife wants to kill me
> 
> 
> 
> 
> haha that's awesome! well one benefit with the extra speed is that you can get out of rough water situations faster, or conversely, enjoy them that much more!
Click to expand...



and benefit 2 is maybe she wont wanna go as much and then you can concentrate on the fish without her yappin your ear off....at least mine does god bless her lol!


----------



## shawnfish

hey Stefan im gonna cross reference that stuff too, not because I think you need help I just like to do it and will in a sober manner this time lol! one plus is when your ready you can have what you find and what I find out and if we both have the same results it maybe give you some reassurance.......oh and did you get my email about the close ups on the tape?


----------



## Plasticmotif

newly listed: 
https://www.ebay.com/itm/CARBURETOR-FOR-A-1997-EVINRUDE-30HP-OUTBOARD-MOTOR-P-N-0435376-/350868278612?pt=Boat_Parts_Accessories_Gear&hash=item51b1610d54&vxp=mtr

I don't think it'll work on my model motor though.


----------



## Plasticmotif

Man, I've been looking on Ebay for ages. I've also been looking on Craigslist and LSN here and can't find anyone to even trade with. 

I guess 30/35 Tillers aren't common around me. Find the carb for my year motor isn't easy either.

Bah!


----------



## shawnfish

[url=https://www.tinboats.net/forum/viewtopic.php?p=328852#p328852 said:


> Plasticmotif » 09 Sep 2013, 21:34[/url]"]Man, I've been looking on Ebay for ages. I've also been looking on Craigslist and LSN here and can't find anyone to even trade with.
> 
> I guess 30/35 Tillers aren't common around me. Find the carb for my year motor isn't easy either.
> 
> Bah!


what carb are you looking for?


----------



## longshot

I got mine from boats.net


----------



## T Man

A 5hp gain almost doubled top end? This seem off to anyone else but me?


----------



## Plasticmotif

Ive got a 90 20 hp. I've bored it to the same as OP. I'd like more power. So, anything above 25 that'd work on my motor. 

Also, T man of you're not able to plane the boat you'd notice a big difference.


----------



## Plasticmotif

My diligence paid off. 

Just got this: https://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=111168222610

Asking if he's got a 30 HP intake to go with it.


----------



## Plasticmotif

I had a chance to take my boat out to a proper lake today. Previously, I was only able to do about 16-17 mph with myself and fishing gear. The boat wouldn't get on plane. It just pushed through the water. I did the carb boring to make my boat a 25. I took it out a few times with the wife and kid on a very small lake (90 acres) It was able to get out on plane but I wasn't able to really run her that well.

Today, I took her out. Motor seems to idle well. Seems to be breathing much better. Motor just flat out sounds better. I verified speed today with GPS again. I was able to get up to get on plane easily and maintain a speed of about 24-25mph. Wide open wasn't much difference. Backing off the throttle some I was able to do 22-24 MPH, wide open 25-26 mph.

That's a significant increase!

I've gotten a 30HP carb and 30 HP intake on the way as well. I'll install them. Hopefully, I'll be able to get about 30 MPH. That's pretty fast. My boat's handling felt great at 25 mph. Well see where the extra 5 horses takes us!


----------



## Stefan

[url=https://www.tinboats.net/forum/viewtopic.php?p=329279#p329279 said:


> Plasticmotif » 14 Sep 2013, 20:00[/url]"]I had a chance to take my boat out to a proper lake today. Previously, I was only able to do about 16-17 mph with myself and fishing gear. The boat wouldn't get on plane. It just pushed through the water. I did the carb boring to make my boat a 25. I took it out a few times with the wife and kid on a very small lake (90 acres) It was able to get out on plane but I wasn't able to really run her that well.
> 
> Today, I took her out. Motor seems to idle well. Seems to be breathing much better. Motor just flat out sounds better. I verified speed today with GPS again. I was able to get up to get on plane easily and maintain a speed of about 24-25mph. Wide open wasn't much difference. Backing off the throttle some I was able to do 22-24 MPH, wide open 25-26 mph.
> 
> That's a significant increase!
> 
> I've gotten a 30HP carb and 30 HP intake on the way as well. I'll install them. Hopefully, I'll be able to get about 30 MPH. That's pretty fast. My boat's handling felt great at 25 mph. Well see where the extra 5 horses takes us!



Thanks for the Update! I've been away for two weeks with no online accessm. I am very happy to read that you have had success with your upgrade and were able to locate a 30 HP carb. ... tHAT is some excellent engine improvement... With regard to your 30 HP carb, and there not being a slow idle screw on it.. I'm not sure how you'd go about adjusting the idle ... I'll see what I can dig up and post what I find.


----------



## Stefan

[url=https://www.tinboats.net/forum/viewtopic.php?p=329279#p329279 said:


> Plasticmotif » 14 Sep 2013, 20:00[/url]"]I had a chance to take my boat out to a proper lake today. Previously, I was only able to do about 16-17 mph with myself and fishing gear. The boat wouldn't get on plane. It just pushed through the water. I did the carb boring to make my boat a 25. I took it out a few times with the wife and kid on a very small lake (90 acres) It was able to get out on plane but I wasn't able to really run her that well.
> 
> Today, I took her out. Motor seems to idle well. Seems to be breathing much better. Motor just flat out sounds better. I verified speed today with GPS again. I was able to get up to get on plane easily and maintain a speed of about 24-25mph. Wide open wasn't much difference. Backing off the throttle some I was able to do 22-24 MPH, wide open 25-26 mph.
> 
> That's a significant increase!
> 
> I've gotten a 30HP carb and 30 HP intake on the way as well. I'll install them. Hopefully, I'll be able to get about 30 MPH. That's pretty fast. My boat's handling felt great at 25 mph. Well see where the extra 5 horses takes us!



Thanks for the Update! I've been away for two weeks with no online accessm. I am very happy to read that you have had success with your upgrade and were able to locate a 30 HP carb. ... tHAT is some excellent engine improvement... With regard to your 30 HP carb, and there not being a slow idle screw on it.. I'm not sure how you'd go about adjusting the idle ... I'll see what I can dig up and post what I find.


----------



## Plasticmotif

I figured it out. It's an 88, not a 91. The low speed idle is set on the top orifice plug location on other years!


----------



## Plasticmotif

So, I figured I'd post some pictures to help out others wanting to do this mod.

After having removed the 20 HP intake, it's clearly throated down. I had already started filing a bit to see how soft the metal was/is. It's soft.
https://img.photobucket.com/albums/v518/plasticmotif/photo_zpsdd0da165.jpg

Difference in carbs. 20HP on top 30 HP on bottom.
https://img.photobucket.com/albums/v518/plasticmotif/photo4_zpscf06ead6.jpg

New intake/Gasket 30HP, much larger:
https://img.photobucket.com/albums/v518/plasticmotif/photo3_zps16f302cf.jpg

Uh oh, some fuel line intake nipples are larger than others. I just forced the line on. Rubber stretches!
https://img.photobucket.com/albums/v518/plasticmotif/photo5_zps163e897b.jpg


----------



## jasper60103

Thanks for sharing. Please let us know how the water test goes.


----------



## Stefan

This is really good stuff. Thanks a lot guys, for posting all of this info for others to benefit... i hope everyone is happy like me with their faster boats that now go on plane!


----------



## Plasticmotif

Well, I hit 30 MPH with the 30!

I was porpoising by myself. I need to change the trim of my motor. *Ran great.* Going to pull the plugs and make sure it's not running too lean or too rich.

It used noticeably more gas!


----------



## Johny25

Get more weight up front if you can.......will help the porpoising


----------



## Siguz

Hi,
I'm new to this forum.
I came across it while looking for a a way to boost the power from my 1989 Evinrude 20hp.

I want to do this manifold modification but I am afraid that no one will work on my motor afterwards.
I'm just starting to learn about small engines but have been working with cars for over 10 years. 

What has to be done after the intake bore?
-Does the timing have to be set differently or anything like that?

I don't want to end up in a spot where regular maintenance is not enough for the motor after it has been changed.

Any input is appreciated.

Thanks!


----------



## Stefan

[url=https://www.tinboats.net/forum/viewtopic.php?p=343374#p343374 said:


> Siguz » 19 minutes ago[/url]"]Hi,
> I'm new to this forum.
> I came across it while looking for a a way to boost the power from my 1989 Evinrude 20hp.
> 
> I want to do this manifold modification but I am afraid that no one will work on my motor afterwards.
> I'm just starting to learn about small engines but have been working with cars for over 10 years.
> 
> What has to be done after the intake bore?
> -Does the timing have to be set differently or anything like that?
> 
> I don't want to end up in a spot where regular maintenance is not enough for the motor after it has been changed.
> 
> Any input is appreciated.
> 
> Thanks!



Hey,

It depends on the model, year and size of the motor. In my case, the 20 hp was = to the 25, 30 and 35 hp of that vintage. the only difference was the intake manifold and carb for the 30 and 35hp, and for the 25 hp model the only difference was the intake manifold. 

I didnt have to do any further modifications to the engine to get the increased power. 

Again, do your homework on the specific motor you would be modding. Luckily for me , my engine shared a powerhead and gearing with many different motors.


----------



## Siguz

I used the Evinrude catalog to compare mine to it's big brother 25.......... All parts match.
I checked mine (E20ECEM) against yours..... we have essentially the same motor when i look at part numbers, except mine is electric start.

My wife won't let me do it unless I'm sure that i can get regular service from a marina when we need it.
There are some things that i can do myself but there are things that i just don't have time to do.

Do you do all your work yourself?


Stefan said:


> [url=<a class="vglnk" title="Link added by VigLink" target="_blank" rel="nofollow" href="https://www.tinboats.net/forum/viewtopic.php?p=343374#p343374 said:
> 
> 
> 
> Siguz"><span>https</span><span>://</span><span>www</span><span>.</span><span>tinboats</span><span>.</span><span>net</span><span>/</span><span>forum</span><span>/</span><span>viewtopic</span><span>.</span><span>php</span><span>?</span><span>p</span><span>=</span><span>343374</span><span>#</span><span>p343374</span><span>]</span><span>Siguz</span></a> » 19 minutes ago[/url]"]Hi,
> I'm new to this forum.
> I came across it while looking for a a way to boost the power from my 1989 Evinrude 20hp.
> 
> I want to do this manifold modification but I am afraid that no one will work on my motor afterwards.
> I'm just starting to learn about small engines but have been working with cars for over 10 years.
> 
> What has to be done after the intake bore?
> -Does the timing have to be set differently or anything like that?
> 
> I don't want to end up in a spot where regular maintenance is not enough for the motor after it has been changed.
> 
> Any input is appreciated.
> 
> Thanks!
> 
> 
> 
> 
> Hey,
> 
> It depends on the model, year and size of the motor. In my case, the 20 hp was = to the 25, 30 and 35 hp of that vintage. the only difference was the intake manifold and carb for the 30 and 35hp, and for the 25 hp model the only difference was the intake manifold.
> 
> I didnt have to do any further modifications to the engine to get the increased power.
> 
> Again, do your homework on the specific motor you would be modding. Luckily for me , my engine shared a powerhead and gearing with many different motors.
Click to expand...


----------



## Stefan

HI Siguz,

I feel like a bit of an idiot because I didn't read your original post close enough when I replied. I guess I was in a rush... So now that I have time to sit down here is a proper reply. 

You have the exact same motor as me other than the electric start! Amazing motors , they are over engineered and very tough. 

In doing this modification you have absolutely nothing to worry about. All you're doing by boring out the intake manifold is delivering more air to the fuel mixture. I was blown away with the results. If you're hesitating to do the mod, start with taking off the carb and intake manifold. Is the intake manifold obstructed by a key hole shape, like in the pic I posted? If so, then simply bore this out to match the carb opening and your engine will deliver more power.

No marine mechanic would not work on your engine if needed because of this mod. It's not like it has a warranty and it is voided... I did a ton of research on this mod before I did it, on iboats and other boating forums, until I was comfortable. It was definately the right call and I have had no issues with my motor because of it. As a matter of fact, my motor seemed to like the increased air - it's almost like it was starved and underpowered before. 

I live in Gananoque ON, not far from you so, you know where I live, so I have alot to lose suffering your wife's wrath if the mod didn't work... I am certain that it will... Feel free to ask away, I'd be glad to offer my help, and if you want to phone or email me just send a private msg...


----------



## Stefan

Also, have a look at johny25s post on this topic. His post is a lot more detailed than mine with regard to specs and pics and he has a wealth of knowledge on upgrading motors like ours... 

here is the link https://www.tinboats.net/forum/viewtopic.php?f=4&t=23898


----------



## Siguz

I'm starting the mod tomorrow.
I'll try to get as many pictures as I can and also document the process.

Wish me luck and thank for the advice :mrgreen:


----------



## Stefan

Awesome, looking forwrd to hearing about how it goes and the results it achieves for you. just on time for the boating season..


----------



## Siguz

https://drive.google.com/folderview?id=0Bx_nvDyN8sqscXotWW5ETGdvX0k&usp=sharing

The link above is to the pictures of my 20->25 mod.
The pics are numbered in sequence.

You'll notice that I didn't smooth out the opening of the manifold. I didn't because the carb covers all of the rough edges therefore not creating any kind of further turbulence and I wanted to be sure that I had enough material get a proper gasket seal. Also, the marks on the front of the manifold are from my dremel slipping (oops); they are superficial and did not affect the integrity of the surface.

Big thanks to Stefan! Thanks for the idea and thanks for the guidance.

Note: Aluminum melts when a high speed too is used. The best way to do this mod is with a drill press at low speed. I cut is better than many 

Can't wait to get it out on the water


----------



## Stefan

Thank you for contributing to the thread and expanding the knowledge base. You took some great photos that will help other people make this mod... Awesome.! I just know you will be thrilled with the improvement. Let us know how it goes when you get her in the water.


----------



## Siguz

Got my motor started.
Ran like Crap and wouldn't hold idle.
Then I discovered that the carb was set to extra lean.
Turned it up a bit and now we're good to go.
Into the water this weekend.
I'll post performance numbers on the weekend.


----------



## Siguz

What a difference!
gets up to plane with 3 grown men in it!

Top speed is now 38 km/h from 23 km/h with my wife and I in it.
I'd like to get 40 km/h out of it....Any suggestions?


----------



## Stefan

Awesome! I'm glad that it worked! I couldn't beleive it the first time either.

Try this to get over 40km/h:

1-clean and wax the bottom of the boat
2-make sure your prop is in great shape 
3-a dolphin on the bottom of the motor might help

Was your wife happy??? THat's the most important thing


----------



## Siguz

I agree with the Prop..... it needs one for sure.
Unfortunately I used Rock Guard for the bottom because we beach the boat daily.
The Dol-Fin does help a lot. I installed that last year.

Right now I have a 10x3; 3 blade aluminum prop.
What do you think would be a good replacement? What are you running, Stefan?

(Ps Nice to hear from you)


----------



## Stefan

Good to hear from you too... 

I'm using a 10.5 inch 3 blade, which needs to be replaced... I think that the motor can take an 11 inch prop but I have to do more research on that. I have a kicker motor , a 6 hp on my boat that I use for trolling and sometimes when I am going long distances i start them both. 

THe throttle on the 6 hp is stiffened to stay at constant speeds. I open it right up in conjunction with the big motor and it gives it a serious boost, probably 7 km/h more. 

Are you going to be fishing on the St Lawrence at all this summer?


----------



## Stefan

Good to hear from you too... 

I'm using a 10.5 inch 3 blade, which needs to be replaced... I think that the motor can take an 11 inch prop but I have to do more research on that. I have a kicker motor , a 6 hp on my boat that I use for trolling and sometimes when I am going long distances i start them both. 

THe throttle on the 6 hp is stiffened to stay at constant speeds. I open it right up in conjunction with the big motor and it gives it a serious boost, probably 7 km/h more. 

Are you going to be fishing on the St Lawrence at all this summer?


----------



## Siguz

I spoke with some Evinrude dealers and they've advised me to try a 10 x 15, 3 blade.
They said that going to an 11 would slow the acceleration to a point that I would be unhappy with it.
Even going to 15 pitch will reduce the acceleration but they said it would still be okay.

Now..... to find a prop that doesn't cost sooooo much especially when all of this is a gamble.

Would anyone recommend a particular supplier or brand that won't break the bank?


----------



## Johny25

Ok hold up! I am sorry but I have to interject some knowledge here. First off the dolphin will not help top speed at all.....sorry. It helps keep boat on plane at lower speed and helps boat plane out, no top end increase. In fact it can do the opposite to top speed if not set up correctly. 

Second if you want the correct prop to get top speed then post your current prop specs, RPM, GPS speed and make and model of motor. This will let me know your gear ratio and recommended RPM for the motor to give you a better idea of correct prop now that you did mods to engine. 

DO NOT BUY A PROP BECAUSE SOMEONE TOLD YOU OVER THE PHONE IT WOULD BE OK! TRUST ME.....You have a high risk of wasting your money and messing up your motor. They are designed to run at a specific RPM range and just guessing without proper info can take away life of your motor or ruin it entirely


----------



## Stefan

[url=https://www.tinboats.net/forum/viewtopic.php?p=353935#p353935 said:


> Johny25 » Today, 19:20[/url]"]Ok hold up! I am sorry but I have to interject some knowledge here. First off the dolphin will not help top speed at all.....sorry. It helps keep boat on plane at lower speed and helps boat plane out, no top end increase. In fact it can do the opposite to top speed if not set up correctly.
> 
> Second if you want the correct prop to get top speed then post your current prop specs, RPM, GPS speed and make and model of motor. This will let me know your gear ratio and recommended RPM for the motor to give you a better idea of correct prop now that you did mods to engine.
> 
> DO NOT BUY A PROP BECAUSE SOMEONE TOLD YOU OVER THE PHONE IT WOULD BE OK! TRUST ME.....You have a high risk of wasting your money and messing up your motor. They are designed to run at a specific RPM range and just guessing without proper info can take away life of your motor or ruin it entirely



Johny25, thanks for imparting your knowledge. I've read numerous of your posts and I know your knowledge of these motors is extensive to say the least.

This is motivating me to replace the prop on my engine. You say that you need the RPM at top speed with current prop.. How do I go about measuring RPM? Is there an aftermarket Tacho tool you can buy and attach to the outboard to give a reading? I've seen them for motorcycles, but is there something similar for outboards? If so, where is the best place to buy these?


----------



## Siguz

[url=https://www.tinboats.net/forum/viewtopic.php?p=353949#p353949 said:


> Stefan » 28 May 2014, 21:47[/url]"]
> 
> 
> [url=https://www.tinboats.net/forum/viewtopic.php?p=353935#p353935 said:
> 
> 
> 
> Johny25 » Today, 19:20[/url]"]Ok hold up! I am sorry but I have to interject some knowledge here. First off the dolphin will not help top speed at all.....sorry. It helps keep boat on plane at lower speed and helps boat plane out, no top end increase. In fact it can do the opposite to top speed if not set up correctly.
> 
> Second if you want the correct prop to get top speed then post your current prop specs, RPM, GPS speed and make and model of motor. This will let me know your gear ratio and recommended RPM for the motor to give you a better idea of correct prop now that you did mods to engine.
> 
> DO NOT BUY A PROP BECAUSE SOMEONE TOLD YOU OVER THE PHONE IT WOULD BE OK! TRUST ME.....You have a high risk of wasting your money and messing up your motor. They are designed to run at a specific RPM range and just guessing without proper info can take away life of your motor or ruin it entirely
> 
> 
> 
> 
> Johny25, thanks for imparting your knowledge. I've read numerous of your posts and I know your knowledge of these motors is extensive to say the least.
> 
> This is motivating me to replace the prop on my engine. You say that you need the RPM at top speed with current prop.. How do I go about measuring RPM? Is there an aftermarket Tacho tool you can buy and attach to the outboard to give a reading? I've seen them for motorcycles, but is there something similar for outboards? If so, where is the best place to buy these?
Click to expand...



I've read many posts from both you guys and you are the ones that have inspired me to learn more about these motors.

Johny25:
I agree the Dol-fin does not help top speed in any way but it does help get up to plane much quicker.

As Stefan asked; how can we check our RPM without any gauges?
It surely doesn't sound like it's over/under reving.

The only mod that I've done is the intake manifold.
-Currently running a 10in 13p 3blade
I looked online at the evinrude parts catalog and it listed a 10*15 prop suitable for the motor.
-Model# CE20TECEM (E20ECEM)
-1989 eveinrude 20hp (thru-hub)
-GPS speed is 38km/h 

Thank you for your input


----------



## Linhardt

https://www.tinytach.com/gasoline.php

This will get your RPM for you. From what I have seen it is very simple to use, but I have never used it myself. I think it is as simple as wrapping the red wire lead around the spark plug wire and grounding the other wire, or something like that. Check around and you might find it cheaper on other websites.


----------



## Siguz

[url=https://www.tinboats.net/forum/viewtopic.php?p=354019#p354019 said:


> Linhardt » 29 May 2014, 11:12[/url]"]https://www.tinytach.com/gasoline.php
> 
> This will get your RPM for you. From what I have seen it is very simple to use, but I have never used it myself. I think it is as simple as wrapping the red wire lead around the spark plug wire and grounding the other wire, or something like that. Check around and you might find it cheaper on other websites.



Very neat!
I'll see if I can find it in Canada. I hate ordering stuff like this from across the border because of warranty and shipping hassles.
Thanks


----------



## Stefan

[url=https://www.tinboats.net/forum/viewtopic.php?p=354019#p354019 said:


> Linhardt » 56 minutes ago[/url]"]https://www.tinytach.com/gasoline.php
> 
> This will get your RPM for you. From what I have seen it is very simple to use, but I have never used it myself. I think it is as simple as wrapping the red wire lead around the spark plug wire and grounding the other wire, or something like that. Check around and you might find it cheaper on other websites.




Thank you for the info... I am going to talk to a buddy of mine who is into all of this stuff and see if he has one.. If not, I'll go make the purchase


----------



## Johny25

[url=https://www.tinboats.net/forum/viewtopic.php?p=354019#p354019 said:


> Linhardt » Today, 07:12[/url]"]https://www.tinytach.com/gasoline.php
> 
> This will get your RPM for you. From what I have seen it is very simple to use, but I have never used it myself. I think it is as simple as wrapping the red wire lead around the spark plug wire and grounding the other wire, or something like that. Check around and you might find it cheaper on other websites.



Correct ^^^^ I have this exact tach for my smaller motors and it works great and very easy to use and worth the $50 bucks or so. I bought mine off of ebay so I know you can get them in Canada.


----------



## Johny25

So you have an 89' 20hp which you turned into a 25hp correct. The 20 and 25hp have same recommended RPM range 4500-5500 RPM in that year. My advice would be to get real close to the 5500 RPM when you have the lightest load you typically run in your boat. And don't worry if you turn 5600-5800 it won't hurt these motors. In fact the 30hp runs at 5800 and it is just different carburetor. 

Your gear ratio is a 13:28 also known as 2.15:1

Get a tach and we can help you get the correct prop. But by looking at the info you already have given me I think you may be OVER propped already.

If you are doing 38kmh (23.5mph in my language lol) with a 2.15:1 gear ratio and a 13 pitch prop then it is HIGHLY likely you are only running at around 4700-4800 RPM. These motors produce the 25hp at 5000-5200 and run way better over 5000k


----------



## Siguz

Got a tach. Will test tonight or tomorrow.
Which cylinder do I test.. 1 or 2?


----------



## Siguz

[url=https://www.tinboats.net/forum/viewtopic.php?p=354109#p354109 said:


> Johny25 » 30 May 2014, 02:14[/url]"]So you have an 89' 20hp which you turned into a 25hp correct. The 20 and 25hp have same recommended RPM range 4500-5500 RPM in that year. My advice would be to get real close to the 5500 RPM when you have the lightest load you typically run in your boat. And don't worry if you turn 5600-5800 it won't hurt these motors. In fact the 30hp runs at 5800 and it is just different carburetor.
> 
> Your gear ratio is a 13:28 also known as 2.15:1
> 
> Get a tach and we can help you get the correct prop. But by looking at the info you already have given me I think you may be OVER propped already.
> 
> If you are doing 38kmh (23.5mph in my language lol) with a 2.15:1 gear ratio and a 13 pitch prop then it is HIGHLY likely you are only running at around 4700-4800 RPM. These motors produce the 25hp at 5000-5200 and run way better over 5000k



So.....
I used an Innova 3568+ timing light/Tach
As Instructed I put the 'clamp' on plug wire #1, and connected it to the battery.
Of course I was running with the hood off but I didn't really have a choice.

I'm supposing that this is wrong but the RPM read as high as 9940 numerous times.......
If this is true shouldn't the motor have blown up by now?
Did I do something wrong? Am I missing something in the equation?

https://plus.google.com/u/0/106046188811399299593/posts
This is a link to the video of the tach going crazy.

What do you think?

Thanks


----------



## rusty503

What it looks like is that it is reading the engine as a 4 cylinder. I read the manual and didn't see a way to change that.


----------



## Siguz

rusty503 said:


> What it looks like is that it is reading the engine as a 4 cylinder. I read the manual and didn't see a way to change that.



That makes sense.
So I guess that means that 1/2 of the reading is the answer.

Thanks very much!


----------



## Siguz

I think I'll try a few more runs tomorrow.
The lake was quite rough tonight.


----------



## Stefan

I am going to get a tach tool .. this is interesting.


----------



## Johny25

if it was reading double than your motor would be running 4970rpm which makes sense and would give you a 17% slip ratio.....which is not great. Get a tiny tach and get a good reading. I can assure you that if you buy a 15 pitch you will lug that motor and toast it eventually. You are likely going to end up at an 11 pitch to get RPMs up to par. You must be running a good load in that boat. What kind of boat is it anyway?


----------



## Siguz

[url=https://www.tinboats.net/forum/viewtopic.php?p=354241#p354241 said:


> Johny25 » 31 May 2014, 00:02[/url]"]if it was reading double than your motor would be running 4970rpm which makes sense and would give you a 17% slip ratio.....which is not great. Get a tiny tach and get a good reading. I can assure you that if you buy a 15 pitch you will lug that motor and toast it eventually. You are likely going to end up at an 11 pitch to get RPMs up to par. You must be running a good load in that boat. What kind of boat is it anyway?



Last night I did the run with my wife in the boat running through 2ft waves.
I'm going to run it alone with all my gear today. When I'm alone in the boat the motor has to be at it's lowest trim position to prevent severe cavitation. With a passenger, it runs best up one trim point.
I will measure RPM in both scenarios if the water is calm enough to do so.

What kind of boat?
--- It's a Starcraft. No readable VIn tag so I don't know the year or model. 14.5ft long

Stefan:
What's the pitch of your prop?


----------



## Siguz

Ok
5295 was max RPM
Trim up with 2 batteries full take of gas and fishing gear.
What do you suggest?

Earlier I used cavitation improperly. Should have said porpoising.


----------



## Johny25

Is this how heavy your boat is the majority of the time or do you add more weight usually?

Your numbers come out as follows.....(assuming you are doing 23.5mph still?) you gave RPM and no mph/kph reading so I am going to assume here.

10X13 prop (aluminum?), with a 2.15:1 gear ratio at 5295 RPM and 23.5mph gives you a slip of about 22% which is NOT great by any means. Better to be around 15% on these smaller motors.

My suggestion is if you are going to run any more weight in the boat you definitely have to go down in pitch. A 10X12 prop should get you around the 5500 mark with current setup. Your holeshot will improve and slip will likely drop a bit also. Your speed will not increase though.

If you had bought that 15 pitch you would have lost 400rpm and lugged your motor out. likely not gaining any speed and having a slip number in the upper 20's

Note: this is all speculation as every prop manufacturer has different blade design, rake and cupping which effects RPM and performance. If you go to a stainless prop you may get better performance and RPM with the same pitch prop. But if it has aggressive cupping then it will lower your RPM for same pitch.

I run a 10X14 solas saturn stainless on my 14' Lowe and my boat is pretty heavy with the decking I put in. Sounds like your boat is even heavier and you would not be able to turn a prop that high in pitch.


----------



## Siguz

[url=https://www.tinboats.net/forum/viewtopic.php?p=354700#p354700 said:


> Johny25 » 04 Jun 2014, 16:57[/url]"]Is this how heavy your boat is the majority of the time or do you add more weight usually?
> 
> Your numbers come out as follows.....(assuming you are doing 23.5mph still?) you gave RPM and no mph/kph reading so I am going to assume here.
> 
> 10X13 prop (aluminum?), with a 2.15:1 gear ratio at 5295 RPM and 23.5mph gives you a slip of about 22% which is NOT great by any means. Better to be around 15% on these smaller motors.
> 
> My suggestion is if you are going to run any more weight in the boat you definitely have to go down in pitch. A 10X12 prop should get you around the 5500 mark with current setup. Your holeshot will improve and slip will likely drop a bit also. Your speed will not increase though.
> 
> If you had bought that 15 pitch you would have lost 400rpm and lugged your motor out. likely not gaining any speed and having a slip number in the upper 20's
> 
> Note: this is all speculation as every prop manufacturer has different blade design, rake and cupping which effects RPM and performance. If you go to a stainless prop you may get better performance and RPM with the same pitch prop. But if it has aggressive cupping then it will lower your RPM for same pitch.
> 
> I run a 10X14 solas saturn stainless on my 14' Lowe and my boat is pretty heavy with the decking I put in. Sounds like your boat is even heavier and you would not be able to turn a prop that high in pitch.




Thank you very much for your help.
I'm grateful for your knowledge and guidance.
Weight? I've actually decided to eliminate the trolling motor and extra battery.... save about 100lbs.

We are now thinking about doing the 35hp upgrade.

Other than carb and manifold, are there any other hard components that need to be changed?
..............Should I refer back to your original post, Johny25?


----------



## Siguz

Change of plans...again.....
We're going to keep everything as is and buy the prop.
Found a 10 1/8 x 12 from michigan wheel for $113 from a local boat shop.

Thank you all for your input.

I'll repost once the new prop is installed and run.


----------



## Johny25

Your welcome Siguz......and no, other than the carb and intake you are good to go. IT will actually make it a 30hp though. Not a 35


----------



## Siguz

Prop installed.
Topping out at 24 mph / 38 kph.
Motor sounds healthier now and jumps up onto plane much more quickly.

Are fuel pumps a common problem with these motors?
I think mine is starting to fail.....


----------



## Stumpalump

[url=https://www.tinboats.net/forum/viewtopic.php?p=357496#p357496 said:


> Siguz » 28 Jun 2014, 10:17[/url]"]
> 
> Are fuel pumps a common problem with these motors?
> I think mine is starting to fail.....


If I have this right you basically put a 25hp intake on a 20 hp motor and you are starving for fuel.?.
The 25 may have the same carb or carbs but your main jets are sized for 20 Me thinks....You may be starving for fuel because the main jets are too small causing a lean condition. Swapping jets and putting a fuel pump rebuild kit are simple. The book may even list a different part number for the jets. You let in a lot more air and no more fuel unless I missed that in this long thread. Did you squeeze the bulb when it acted up?


----------



## Siguz

Stumpalump said:


> [url=https://www.tinboats.net/forum/viewtopic.php?p=357496#p357496 said:
> 
> 
> 
> Siguz » 28 Jun 2014, 10:17[/url]"]
> 
> Are fuel pumps a common problem with these motors?
> I think mine is starting to fail.....
> 
> 
> 
> If I have this right you basically put a 25hp intake on a 20 hp motor and you are starving for fuel.?.
> The 25 may have the same carb or carbs but your main jets are sized for 20 Me thinks....You may be starving for fuel because the main jets are too small causing a lean condition. Swapping jets and putting a fuel pump rebuild kit are simple. The book may even list a different part number for the jets. You let in a lot more air and no more fuel unless I missed that in this long thread. Did you squeeze the bulb when it acted up?
Click to expand...

Sorry
I should have clarified.
The motor w as running fine after the mod for about 3 weeks then all of a sudden couldn't hold idle.
Rebuilt the carb.... Ran well again.
One week later.... No power can't plane. 
Found that if I pulled the choke half out it would run better.
All of a sudden runs great again.
In certain there is av few issue.


As for mod.
Carb and jets are the same.
The manifold is also the same but the restriction had been removed.


----------



## Stumpalump

Ethanol fuel that we get today is prone to getting brown jelly like goo in it. Best thing to do as a first step is to give it a fast idle and block one carb at a time with a rag. This creates a high vacuum that will often draw the jelly thru the carb and you won't have to rebuild it. A fresh fuel line is always a good plan if your fighting a problem. I just buy good automotive fuel line and rebuild the bulb by taking apart the check valves in the end and cleaning it all up. Those primer balls will work one minute and not the next. Pull the ends off the bulb and clean it up but don't get the ends swapped. Fuel pump....Is so easy and cheap to rebuild that you might as well knock it out. I don't mess with fuel problems long. I cut my losses and go thru the whole thing once and then I'm done for years. Start with the crap in the bottom of the tank and clean and replace everything you can.


----------



## Johny25

Im guessing the mod has nothing to do with why it is acting up...or it would have happened right away. Could be something as simple as an air leak in the fuel tank line. But it does sound fuel/carb related. Small air leaks can cause havoc


----------



## Siguz

Looks like I got it sorted out.
Rebuilt carb and fuel pump.
Running beautifully again.

I have noticed that the primer needs to 2 pulls to create any vacuum at all. I'll t replace it once the budget allows for it.
Thanks guys


----------



## Johny25

[url=https://www.tinboats.net/forum/viewtopic.php?p=358375#p358375 said:


> Siguz » Today, 06:40[/url]"]Looks like I got it sorted out.
> Rebuilt carb and fuel pump.
> Running beautifully again.
> 
> I have noticed that the primer needs to 2 pulls to create any vacuum at all. I'll t replace it once the budget allows for it.
> Thanks guys



Primer is probably fine........I had to pump mine 3-4 times always first time starting motor


----------



## Siguz

Good to know.
I will double check all the lines though.


----------



## Siguz

Here's a question.....

I was looking through the online parts catalog and noticed that you can buy carb jets suitable for 30-35 HP motors.
Would it make any difference to install these larger jets without replacing the carb itself?


----------



## Siguz

[url=https://www.tinboats.net/forum/viewtopic.php?p=360590#p360590 said:


> Siguz » 23 Jul 2014, 05:40[/url]"]Here's a question.....
> 
> I was looking through the online parts catalog and noticed that you can buy carb jets suitable for 30-35 HP motors.
> Would it make any difference to install these larger jets without replacing the carb itself?



Note: Jets from 20-25 are the same


----------



## Johny25

if you add more fuel you have to add more air......hence the larger venturi on the 30-35 carb


----------



## Siguz

Johny25 said:


> if you add more fuel you have to add more air......hence the larger venturi on the 30-35 carb


Agreed.
I have already punched a few holes in the front of the hood to create somewhat of a 'ram air' setup. I just wonder if it'll be enough air.

I might just spend the 40$ and give it a try.


----------



## Siguz

Installed larger carb today.
Had to cut manifold a little further to accommodate.
I guess I didn't cut it out fully last year.
Hopefully I'll be able to get on the water before the end of the month.
Water levels are rising and ice is melting.... Not fast enough though.


----------



## EZ707

Thats fun. I had a 35 hp carb on that same motor and i love it


----------



## Siguz

got the Carb on.
41km/h with a 10x12 prop.
Gonna try a 10x13 and see what happens
Motor seems to run better now that there are no restrictions.


----------



## EZ707

Very nice! Im thinking of doing the 10x13 prop myself. Let me inow how it works out


----------



## Siguz

43 with the 10x13.
I think it can probably handle 10x14 but that depends on each application.


----------



## Randolphdmobius

I found a 25hp carb and intake for my 1982 20hp and do a similar mod.
My engine has a reducer elbow on the fuel line from pump to carb, (I assume all the 20hp engines from this era do), would anyone know if it’s wise to replace this with a larger fuel hose and do away with the reducer?


----------



## RaisedByWolves

Dont know why the quote function changed....



> My engine has a reducer elbow



A pic or some size reference would go a long way here, but I dont think there would be much of an issue using what's there as restricting fuel for whatever purpose from the factory would be odd.

Ie, The high speed jet is relatively tiny in comparison to most fuel line.


----------

