# 30HP 2 stroke Johnson prop ?



## 1648grizz (Jun 12, 2019)

Was there a standard prop that came with this engine new ? Would a 10x15 work ok on 1648 with light load ?

Thanks Bill


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## Weldorthemagnificent (Jun 12, 2019)

Probably work fine if it's just one guy. I have a 16' and run a 10x13 which revs right out if I'm alone which is seldom and will still get on plane with 3 guys and gear. 

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## 1648grizz (Jun 12, 2019)

Weldorthemagnificent said:


> Probably work fine if it's just one guy. I have a 16' and run a 10x13 which revs right out if I'm alone which is seldom and will still get on plane with 3 guys and gear.
> 
> Sent from my CLT-L04 using Tapatalk



I have a 2005 25HP 2 stroke Johnson ,ordered a 30HP carb and 10x15 prop. I clocked my top speed at 29-30 mph with just me with 10x13 prop, hoping to gain more top end with 30HP carb and 10x15 prop.


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## GYPSY400 (Jun 12, 2019)

15" on a 30hp will be at the top limit of what the motor can handle.. if it's a light load you should be ok..
For reference I'm running a 10x11" on a 16ft v bottom with floors, livewell, bow mount and 2 batteries.. with my dog and I, I'm turning 5700rpm and 45km/h

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## Pappy (Jun 12, 2019)

Rather see a 13 on it than a 15. Will be a better all around prop for you with varying loads.


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## 1648grizz (Jun 12, 2019)

Pappy said:


> Rather see a 13 on it than a 15. Will be a better all around prop for you with varying loads.



Yes will still have the 13 for heavy loads but when alone I want top speed . I met a friend out on the water last week. He just bought a new 1648 with 40HP 4 stroke Merc . His boat was about 2 or 3 mph Quicker then mine, I can't allow that lol


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## 1648grizz (Jun 19, 2019)

Well got new 30HP carb on my 25HP 2005 Johnson part #0439377 big difference in throttle response but did not notice any more top end speed between OEM 10x13 prop that came with the engine and the new Solas 10x15 I just bought. could that be because it's a Solas prop ?
Topped out at 25mph with two people with both props .


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## RaisedByWolves (Jun 19, 2019)

Im looking into putting a 35hp carb on my 25 evinrude and Im finding there is more to it than just the carb.

For my motor I need to add the correct reed box/intake and possibly the tuner inside the leg.

Your RPMs are limited (6200?/6500?)so once you get it tuned to where you are hitting the limiter you then need to go up one size (2") pitch on the prop.

Do you have a way to monitor RPM?

How deep is your motor sitting?

And last, where did you find the carb?


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## 1648grizz (Jun 19, 2019)

RaisedByWolves said:


> Im looking into putting a 35hp carb on my 25 evinrude and Im finding there is more to it than just the carb.
> 
> For my motor I need to add the correct reed box/intake and possibly the tuner inside the leg.
> 
> ...


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## RaisedByWolves (Jun 21, 2019)

RaisedByWolves said:


> Im looking into putting a 35hp carb on my 25 evinrude and Im finding there is more to it than just the carb.
> 
> For my motor I need to add the correct reed box/intake and possibly the tuner inside the leg.
> 
> ...





1648grizz said:


> I have a tach on order , I believe the RPM max for my 2005 25HP is 5500 , My engine plate sits flush with bottom of boat .Bought the carb from Dusky Marine online down in FL $275 ,they had 8 on the shelf. I cross referenced my 25HP to the 30HP same intake and reeds.



8 on the shelf is good, $275 each? Ooof! :shock: 

Is that a 30hp carb or a 35hp?

Ill have to look it up again, but on another forum there is talk about two different ignition power packs, one limiting rpm to 6200 and the other having no limit.

Is there a number on the side of yours?

The 6200 should have that number on the outside of it somewhere so maybe the 5500 does also.

RPM is going to be the key to going faster.


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## 1648grizz (Jun 22, 2019)

RaisedByWolves said:


> RaisedByWolves said:
> 
> 
> > Im looking into putting a 35hp carb on my 25 evinrude and Im finding there is more to it than just the carb.
> ...


My 25HP is a 2005, the last year for the 25HP 2 stroke Johnson I believe. I definitely got a better hole shot, the bay was choppy so top end could have been better. I'll be out tomorrow in the creek to get a better top speed test with both props. As far as max RPM I'll know tomorrow as I have a tach now.

I read that the RPM range for my engine is between 4500 and 5500 and exceeding 5500 could damage the engine . I also read here on the forum that a 35HP from the 80s is a 30HP of today. I read a post here from (skids) he has a 2001 25HP, put the 30HP carb on only and gained about 5 mph on top end .
If I can get that I'll be pushing 35mph.... will post results tomorrow.... Part # 0439377 is a 30HP carb . I just checked the part # for my power pack, same # as 2005 30HP. Did have a (6100) # next to it, maybe the RPM limit ?


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## RaisedByWolves (Jun 22, 2019)

Yeah, I was just tinkering on mine and came across that same number, which should indicate that 6100 is the limit on that powerpack.

If you go over to Boatracingfacts.com and look in the tech page you will find the thread Im following regarding mods. You are looking for the 31.8 engine thread as that is how they refer to them due to them being 31.8ci displacement.

Those guys are running 6500-6800rpm at 45mph+ with their racing hulls and without any immediate negative effects.

Following the oem recommendations will certainly give you a longer life for your motor, but what fun is that? :wink: 


There is a whole slew of things you can do for a higher top end speed, some of which seem counter intuitive like jacking up the engine (Airing out the prop) and trimming it to get you to those higher numbers.

Between the thread here by Johnny25 and the 31.8 thread at BRF just about everything motor/prop wise is covered.


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## Weldorthemagnificent (Jun 22, 2019)

It takes roughly twice the horsepower to go half again as fast so don't expect huge gains. I went from a 25 to a 35 (1983 so powerhead HP) and top speed with a 13 pitch prop is very close. What it does do is come out of the hole like jack the bear and will even get up on plane with 3 big boys and all the camping gear we can pile on. If you want to pick up more jam, look for a Nissan/Tohatsu m40c or a Yamaha/mariner 2cyl 40. Both are light weight for a 40 and good reliable motors. 

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## 1648grizz (Jun 22, 2019)

I have a 2005 1648 Grizzly with the 15" transom ,max HP rated at 30 for the boat. Can you buy a new 40HP engine with the 15" shaft ?


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## RaisedByWolves (Jun 23, 2019)

Weldorthemagnificent said:


> It takes roughly twice the horsepower to go half again as fast so don't expect huge gains. I went from a 25 to a 35 (1983 so powerhead HP) and top speed with a 13 pitch prop is very close. What it does do is come out of the hole like jack the bear and will even get up on plane with 3 big boys and all the camping gear we can pile on. If you want to pick up more jam, look for a Nissan/Tohatsu m40c or a Yamaha/mariner 2cyl 40. Both are light weight for a 40 and good reliable motors.
> 
> Sent from my CLT-L04 using Tapatalk




Huge gains aside, you didnt follow through with your swap is you didnt find the right prop for your combo.

A 10.5 x 13 prop turning 5800rpm will give you the same top speed whether is is backed by a 20hp motor or a 70hp motor. Actually the 70hp will be slower due to the added weight. #-o 

Prop pitch vs RPM.


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## Weldorthemagnificent (Jun 23, 2019)

I felt a 15 pitch wouldn't be ideal for my boat as I am never alone in it. Usually at least one big boy and often two plus gear. When loaded it runs as it should. Now if the coin were flipped and I fished alone often, it would wear a 15

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## 1648grizz (Jun 24, 2019)

27mph with the 10x13 and the 10x15. My RPM was 5335 wot with just me in the boat.
When the boat and motor was new in 2005 my little yellow Garmin GPS read 29 to 30 mph.
Maybe the Garmin lied or the engine lost some compression over the years .
But definitely gets up on plane much better with the 30HP carb.


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## 1648grizz (Jun 27, 2019)

Raised the motor up 1" gained 2 mph . 29mph , guess that's all I'm gonna get with a 30hp on a 1648 Grizzly.


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## Matt193 (Jun 27, 2019)

I have the same setup as you; a 30 HP carb on a 25 HP motor on my 16' Sylvan Sport Troller. I can get 30-31 with a good stainless 13p prop but 28-29 mph with various aluminum ones. I have a 30 HP intake that I need to install and also swap out the throttle cam off of a 35 that we use for parts to see if that makes any difference and then I might be able to pull a 14p or 15p prop.

Right now I'm running into a lean spot at about 3000 RPM which is annoying and I'm hoping one of those two items solves it.

I don't know what the difference is between the 25 and 30/35 cam. I'm assuming the profile might be slightly different, which I'm hoping to find out as soon as I get a spare minute to go over and pull it from the junker.

I also might try a set of CCMS reeds, but I don't want to start modding until I get the motor running correctly stock.


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## 1648grizz (Jun 27, 2019)

Matt193 said:


> I have the same setup as you; a 30 HP carb on a 25 HP motor on my 16' Sylvan Sport Troller. I can get 30-31 with a good stainless 13p prop but 28-29 mph with various aluminum ones. I have a 30 HP intake that I need to install and also swap out the throttle cam off of a 35 that we use for parts to see if that makes any difference and then I might be able to pull a 14p or 15p prop.
> 
> Right now I'm running into a lean spot at about 3000 RPM which is annoying and I'm hoping one of those two items solves it.
> 
> ...


How much top end did you gain with the carb swap ? I didn't check top end before the swap but when boat was new I hit 29 to 30 mph


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## Matt193 (Jun 27, 2019)

3-5 mph depending on the prop. #-o When it was a 25, I was running a 11p prop and would hit 24-25 mph at 5650 rpm, which was most efficient one for my setup. With the 30 carb, it has much more torque and will hit the rev limiter at a little over 3/4 throttle with just me in the boat. With two people in the boat, it'll run 27 mph and 5700 rpm, which is pretty much spot on. I didn't try the stainless prop with two people to see how much speed and rpm I lost. I wanted to see what kind of gains I would get with just changing out the carb and then see if I gained anything with the intake and cam. One racing forum says the intake really doesn't make a difference, but there is a slight amount of restriction on mine yet plus the 30 hp intake has more volume, so I'm interested to see for myself. 

I just want to be able to beat my friend with his 25 hp 3 cyl OMC on a 16' jon which is about 2 mph faster than me yet.


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## 1648grizz (Jun 27, 2019)

lol, I also have a friend with a new 1648 and 40 Merc I'm trying to keep up with, he tops out about 33 mph
My boat is about 400lbs , motor 150lbs, me 225lbs 3 gallon tank and battery max RPM with 10x13 was 5330 at 27mph . 10x15 prop 4850 at 27mph . Does this sound about right for the weight I'm trying to push ?


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## RaisedByWolves (Jun 28, 2019)

Its certainly in the ballpark.

With my stock 25 I was just hitting 28 with 27 steady on a 14' Mirrocraft, me at 310, fuel, battery and trolling motor.

And my prop is a mess.

I had it out with that loadout plus the wife last weekend with a tach installed and we were going 25 @ 5750Rpm.

I have two better props coming so Im hoping for 30 with just me.

With my current prop I may hit the rev limiter. It was all beat to hell when I got the motor and I rehabbed it a bit, but it will never be right without a lot of work.

Grizz, try the 15P and keep raising the motor.


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## Matt193 (Jun 28, 2019)

I agree with raisedbywolves. I think you're close and it's all about trying different things at this point and seeing what works and go from there.


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## 1648grizz (Jun 29, 2019)

Matt193 said:


> I agree with raisedbywolves. I think you're close and it's all about trying different things at this point and seeing what works and go from there.



My cav plate is 1" out of the water WOT, the water pickup is still completely submerged . My plugs look wet I may by running way to rich, should the plugs look wet ? When I go in with the adjustment screw it starts to sputter at low idle , but it does rev up better. What is the best way to set low idle adjustment ?


Thanks


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## GYPSY400 (Jun 29, 2019)

1648grizz said:


> Matt193 said:
> 
> 
> > I agree with raisedbywolves. I think you're close and it's all about trying different things at this point and seeing what works and go from there.
> ...


The plugs should be dry and chocolate brown..
the best way to adjust low speed is to adjust it in until it runs rough... then adjust it out until it runs rough.. then set it in the middle of those two settings.. motor needs to be in gear and up to operating temp.

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## RaisedByWolves (Jun 29, 2019)

1648grizz said:


> Matt193 said:
> 
> 
> > I agree with raisedbywolves. I think you're close and it's all about trying different things at this point and seeing what works and go from there.
> ...



1" out of the water or 1" above the bottom of the boat?

Theres a big difference.

Im @ 1" above the bottom of the boat and my cav plate is still buried at WOT.


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## 1648grizz (Jun 29, 2019)

RaisedByWolves said:


> 1648grizz said:
> 
> 
> > Matt193 said:
> ...


1" above bottom of boat where I have the trim set. 1" below cav plate WOT


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## 1648grizz (Jul 7, 2019)

Put 10x13 stainless on topped out at 30 mph at 5510 rpms WOT . Got up on plane vary nice no cavitation like I was getting with the aluminum props.
The bay was a little choppy so might do a little better on top end.


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## RaisedByWolves (Jul 7, 2019)

1648grizz said:


> Put 10x13 stainless on topped out at 30 mph at 5510 rpms WOT . Got up on plane vary nice no cavitation like I was getting with the aluminum props.
> The bay was a little choppy so might do a little better on top end.



Can you post a pic of your aluminum props blades edge on?

Im having some trouble with cavitation @ around half throttle if I goose it and Im wondering if it is due to how thin my blades are or if the blades on my other prop is too thick.


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## 1648grizz (Jul 7, 2019)

RaisedByWolves said:


> 1648grizz said:
> 
> 
> > Put 10x13 stainless on topped out at 30 mph at 5510 rpms WOT . Got up on plane vary nice no cavitation like I was getting with the aluminum props.
> ...



The old 10x13 that came with the motor new , never hit nothing hard with it but did chew the bottom up often duck hunting. I think I know why my boat did 29 to 30 mph when it was new, looks like I may have a few hundred LBS of water logged foam in the bench seat and front deck.


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## Weldorthemagnificent (Jul 7, 2019)

You aren't over revving so that's good. Soaked foam can make a huge difference!

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## RaisedByWolves (Jul 8, 2019)

That’s about what my “new” prop looks like. I’m going to try it out at different heights to see if it will stop cavitating While still making good speed.

My current prop and my get home prop are more........ interesting looking?

One has no cup and the other, well, lets just say it’s a lot lighter than it should be and judging by your speed/rpm numbers both of my props suck.

Thanks for the pic.


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## RaisedByWolves (Jul 16, 2019)

Took my “new” prop for a ride Sunday and man what a difference a prop can make!

I haven’t really cleaned it up much save for knocking some dings back into shape, but even at that it’s a night/day difference.

I only gained 2mph loaded, and nothing with just me in it(scratches head) but my hole shot is now incredible and no more cavitation if I goose it while on plane.

Even though I gained on my top speed loaded, my wot RPMs stayed the same. That plus the fact that my wot speed with only me in it didn’t change makes me think I’m hitting the rev limiter or the limits of the carb/intake.

27mph @5740rpm

I did pick up a carb off of a 70hp that will fit but I need to look into the jetting and clean it up before trying it.


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