# Jack Plate Installed w/ Pic, REV tested and need some advice



## therobzilla (Aug 11, 2013)

Thanks for everyone input, here is what I did, copied the design by looking at others posts, adjusted it for my application.

































Took longer for the Spar to dry than it did to but the thing together.

Thanks everyone for there help.

Ready for fishing now, just have to get my truck back from the bodyshop, got in a little fender bender last week. 

Rob


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## longshot (Aug 11, 2013)

Nice job. I put a th mini jacker on mine. But I like the adjustability of your design


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## PATRIOT (Aug 11, 2013)

Nice woodworking but . . . I gotta ask . . . any reason why you didn't go with aluminum throughout? :?: :?: :?: :?: :?: :?: :?:


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## therobzilla (Aug 11, 2013)

[url=https://www.tinboats.net/forum/viewtopic.php?p=325652#p325652 said:


> PATRIOT » 44 minutes ago[/url]"]Nice woodworking but . . . I gotta ask . . . any reason why you didn't go with aluminum throughout? :?: :?: :?: :?: :?: :?: :?:




Fair question, I used wood as the backing on the transom as i work with wood more than aluminum, and feel as long as the wood is treated well it lasts and I think provides more strength. 

As far as the actual where the motor will hang from, the motor has little teeth that when clamped to the wood mount, I feel won't move as much as if mounted to aluminum. 

The other thing, my boat has a custom cover for it, and my motor comes off after each trip and is stored in the boat under the cover.


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## RAMROD (Aug 12, 2013)

Very nice jack plate! That transom looks identical to the one in my 12 footer the only thing I wish I would have done different is extend the inside brace all the way across.


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## tomme boy (Aug 12, 2013)

Looks great! One suggestion. Put a flap of some sort on the inside. The first time you try to reverse with a little throttle. Like trying to get off the trailer. Water will shoot up the jackplate and fill your boat.


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## Whoopbass (Aug 12, 2013)

Looks almost identical to the one I built. The issue I had with mine is that all I could get was 3" angled aluminum. I figured it would be ok but after I mounted the outboard and lowered it the transom clamp screws hit the transom before I could get it lowered enough. It would work fine if I built it for a long shaft or jet motor but I was just trying to raise the motor some and give it some set back. I ended up removing the stock screws and using some bolts that tightened down using an allen wrench.
I don't think there was any performance gained and having to reach back a few extra inches was sort of a pain so I ended up removing it. It did look good on the back of the boat though......
Nice job =D>


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## ckr74 (Aug 12, 2013)

[url=https://www.tinboats.net/forum/viewtopic.php?p=325673#p325673 said:


> tomme boy » Today, 01:03[/url]"]Looks great! One suggestion. Put a flap of some sort on the inside. The first time you try to reverse with a little throttle. Like trying to get off the trailer. Water will shoot up the jackplate and fill your boat.


Mine's almost exact same and I never had issues. They do look good but I don't know about performance gains. I doubt ther is much.


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## Attwanl (Aug 12, 2013)

That looks great!..mind if I copy that for my boat.


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## therobzilla (Aug 12, 2013)

[url=https://www.tinboats.net/forum/viewtopic.php?p=325789#p325789 said:


> Attwanl » 13 minutes ago[/url]"]That looks great!..mind if I copy that for my boat.




No problem, I got the idea from some pictures I saw online, so it's really not my idea... LOL 

Motor hanging wood, is two pcs of 3/4" exterior plywood laminated together, with 9 coats of Helmsman Spar on it.
Angle is 2 1/2" x 2 1/4" x 1/4"

Enjoy, it was a fun project.

Rob


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## therobzilla (Aug 12, 2013)

[url=https://www.tinboats.net/forum/viewtopic.php?p=325674#p325674 said:


> Whoopbass » Today, 01:39[/url]"]Looks almost identical to the one I built. The issue I had with mine is that all I could get was 3" angled aluminum. I figured it would be ok but after I mounted the outboard and lowered it the transom clamp screws hit the transom before I could get it lowered enough. It would work fine if I built it for a long shaft or jet motor but I was just trying to raise the motor some and give it some set back. I ended up removing the stock screws and using some bolts that tightened down using an allen wrench.
> I don't think there was any performance gained and having to reach back a few extra inches was sort of a pain so I ended up removing it. It did look good on the back of the boat though......
> Nice job =D>



My motor to transom length is way off, long shaft, short shaft, whatever shaft.... LOL The boat is forever old, I wanted to make sure that there were not any gains or losses with the length of the motor vs the boat, so I decided to build the plate, it really was not a huge deal, I got the angle for nothing and made the wood with material I had laying around, the longest part of the whole ordeal was waiting for the Spar to dry between coats.

My plan is to set up the motor at the stock position on the transom as it would sit without the plate, and check RPM's vs. motor speed via GPS and Tach. and then work from there, the motor height vs. transom are grossly off based on everything I have read on this site and others. Everyone is saying even or and 1" higher than bottom of transom. That's not the case for me. I plan to make multiplier passes with adjusting the motor height until I have reached it's worst case scenario and then make the correct decision based on the specific runs with the Tach and GPS. 

It's not a huge deal but it's kind of interesting in my mind. If there are gains to be had by using the plate, I will surely find out, if not, no major loss, I was bored this weekend as my truck was in a little fender bender last week and it's not towing my boat anywhere soon.






Thanks for the feedback, I will keep the thread posted as to if any performance is gained by the adjustments.

Rob


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## Charger25 (Aug 13, 2013)

"My plan is to set up the motor at the stock position on the transom as it would sit without the plate, and check RPM's vs. motor speed via GPS and Tach. and then work from there, the motor height vs. transom are grossly off based on everything I have read on this site and others. Everyone is saying even or and 1" higher than bottom of transom. That's not the case for me. I plan to make multiplier passes with adjusting the motor height until I have reached it's worst case scenario and then make the correct decision based on the specific runs with the Tach and GPS. "

Now THATS the way ya do it !! Every hull is different , every motor, prop, every set up is different. You just got find out what works best for you configuration. :beer:


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## Pappy (Aug 15, 2013)

To the OP.....Great job on the plate. Two of the side benefits of placing the wood between the plates are that wood will provide a good "grip" for the engine clamped to it and secondly the wood provides sound deadening between the engine and hull. Now I am going off topic a little..............

There are ALWAYS gains to be made with raising the static transom height of an engine. For those who claim not to have realized those gains.........you did not complete your work to make it perform. 
Propellers must be modified or substituted when raising small "kicker" style engines on transoms. What you have to remember is that the OEM designed these engines and propellers to function in a fully submerged application. You have just changed the ball game for those parts and pieces. Up to several tries or modifications may be necessary to propellers depending on your boat/load/load placement. 
There are long winded threads on here outlining success stories and what it took to make it happen. Look them up.


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## flatboat (Aug 18, 2013)

just curious how it ran and what you ended up with , hight wise


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## therobzilla (Aug 19, 2013)

[url=https://www.tinboats.net/forum/viewtopic.php?p=326465#p326465 said:


> flatboat » Today, 10:00[/url]"]just curious how it ran and what you ended up with , hight wise




Had all the best intention to getting it out this weekend, but it never happened, ran into a few snags. When I got the motor, the prop was all torn up, so I had it rebuilt, Props Plus is right here in Scottsdale, AZ and for $42.00 to have it repaired I cold not resist, considering I may change depending on what and how it runs. So went to put the prop back on and noticed the thrust washer before the nut was all torn up. I did not find this out until too late, and the local parts house was closed....... So that delayed the testing. 

I also have a buyer for my other motor, Merc 1979 7.5 hp, and went to start it in the garbage can and get things running and ready for the buyer, and the pull rope snapped........ [-o< , things just were not going my way this weekend. Rewinding that starter spring and assembly on the Merc is a PITA, so off to my marine mechanic buddy for repair. The buyer will be here on Friday, and I have to leave Monday for a "Business Trip", I'm taking a customer and myself Salmon Fishing on the Sacramento River north or Redding, CA for 3 days of float fishing, they are catching 30 to 50 pounders right now, so thing are going have to wait until next weekend.........

Long winded answer to, I have not put it back in the water yet...... :mrgreen: 

I have a very specific plan on adjusting the motor height and I have borrowed a couple of diffrent props from the prop store for testing purposes, including a SS one. I'm keeping detailed notes on each pass, and will test each setup. I'm probably going to spend most of the day back and forth to the ramp, but I will get this sucker dialed in and report back how I did it.

Thanks for asking..... :mrgreen: 

Rob


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## therobzilla (Aug 25, 2013)

OK,

Calling out all you prop experts, finally had some time today to take the boat out and do some testing and adjustments and took some notes.

Basics:
* Boat is a 12' Game-fisher V hull.
* Boat weight, with myself full fuel and all my "Stuff", +- 375/400 lbs with motor
* Motor is a Johnson 1986 15 HP
* Current prop on it is a 9 1/2" x 10 pitch
* Testing was done at 1200 ft elevation above sea level.
* Standard Jetting, (See Special Note Below)
* I don't know the gear ratio of the motor, sorry.

Made numerous passes, and found the correct height for the motor above the transom, without cavitation and getting on plate quickly.

Test Run's Results:
* Optimal Pass without cavitation and slip at prop due to height of motor vs. bottom of hull height:
* 6420 RPM at WOT, GPS speed at 21 MPH, this is with motor in first position on tilt setting.

Other passes:
* Did not think these passes were quite optimal as the cavitation due to motor height were in excessive however here is the data:
* 6480 RPM at WOT, GPS speed at 23 MPH, with is with motor in the second position on tilt setting. (Lots of cavitation on turns or in the chop, and tons of splash between motor and jackplate)


How I use the boat:
* I mainly use the boat for fishing on the lakes in Northern Arizona, these lakes are at elevations between 5000 ft and 9000 ft and the ones I fish are mainly around 7500 ft in elevation, I use the boat at this elevation about 60% of the time I use the boat. I also use the boat in the bigger lakes in the winter at 1000 ft elevation, and these are big lakes and require covering a large bit of lake to get to the fishing spots. I normally have my son with me when fishing which will add another 150 lb to the overall weight of the boat when used.

*** SPECIAL NOTE ***, currently the boat has standard jets in it, I have not had the ability as of yet to get my hands on high elevation jets for the motor, I know they are available, however I have not found a source for them yet, nor have I found a jetting chart for the Johnson motor yet....

I don't do any trolling with the motor, as use the trolling motor for that.

*** Note *** I have some videos if that will help with suggestions, I will post them on Dropbox and edit this post.


I have some other detail if necessary, however what do you guys think. I would like to hear any suggestions you may have....


* Boat Position In Water *






* Transom Jackplate Positon *





Thanks,
Rob


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## tomme boy (Aug 26, 2013)

You are a little over the 5500 rpm range for the motor


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## therobzilla (Aug 26, 2013)

[url=https://www.tinboats.net/forum/viewtopic.php?p=327375#p327375 said:


> tomme boy » 9 minutes ago[/url]"]You are a little over the 5500 rpm range for the motor




Sorry forgot to state that the cowling sticker has been replaced with a 9.9 sticker for AZ, it's really a 15hp with a 9.9 sticker, the manual say WOT is 6250 on the 15 hp?

Thanks,
Rob


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## Johny25 (Aug 26, 2013)

The sweet spot will be 6250 rpms or that is where you will get the 15 hp from.....anything above or below the motor won't be putting out 15hp although these motors can be run to 7k but I wouldn't do that to my motor personally. My guess is you may get another mph or so by going to an 11 pitch because with the numbers you posted you could turn it right in the sweet rpm area of the motor. Your slip numbers are not great but they are not terrible either for a small motor. It is hard to get under 13% or so with motors of this size. When you get over 20mph with a 15hp you are doing pretty good. Only other way to get more out of it would be to try and move the weight in the boat around or lose some weight entirely. Sounds like you have played with the trim and height of the motor and found how far is to far out of the water already. I would say you are getting just about everything you are going to get out of a 15hp


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## Team Colibri (Aug 26, 2013)

[url=https://www.tinboats.net/forum/viewtopic.php?p=327383#p327383 said:


> Johny25 » Today, 08:11[/url]"]The sweet spot will be 6250 rpms or that is where you will get the 15 hp from.....anything above or below the motor won't be putting out 15hp although these motors can be run to 7k but I wouldn't do that to my motor personally. My guess is you may get another mph or so by going to an 11 pitch because with the numbers you posted you could turn it right in the sweet rpm area of the motor. Your slip numbers are not great but they are not terrible either for a small motor. It is hard to get under 13% or so with motors of this size. When you get over 20mph with a 15hp you are doing pretty good. Only other way to get more out of it would be to try and move the weight in the boat around or lose some weight entirely. Sounds like you have played with the trim and height of the motor and found how far is to far out of the water already. I would say you are getting just about everything you are going to get out of a 15hp



+1


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## therobzilla (Aug 26, 2013)

[url=https://www.tinboats.net/forum/viewtopic.php?p=327386#p327386 said:


> Team Colibri » Today, 00:05[/url]"]
> 
> 
> [url=https://www.tinboats.net/forum/viewtopic.php?p=327383#p327383 said:
> ...




OK, I will think through a 11 pitch prop, however I'm not so sure that the cost of a new prop would be worth the extra mph. I really appreciate you looking at the numbers, I was primarly after someone looking over what I had vs. what would be an ideal setup, and based on what you guys are saying, it looks like I've got the sweet spot setup.

My only other question is how does elevation affect this, when I get to 7500 ft elevation, without different jetting for elevation, won't I loose some power to elevation? I have heard that some guys are making changes in prop for elevation????

Thanks,
Rob


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## Johny25 (Aug 27, 2013)

Yes elevation will have an effect on your motor and you will lose HP the higher you go. My guess is you will see an RPM drop but being you are running 6400 plus already you shouldn't have a problem. I would be interested in seeing the different readings you may get when up that high. I have heard some guys running a lower pitch prop at high altitude to compensate and keep engine in the recommended RPM range.
I am no expert in high altitude operation but the way I understand it the air is less dense and has less oxygen so your motor should run rich. The motor is still pushing same amount of fuel with less oxygen....hence the rich mix. If you always run in high altitude I would suggest running smaller/leaner jets in the carb but be sure and change them back over when coming back to sea level as I believe you can run the risk of burning a cylinder.


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## therobzilla (Aug 27, 2013)

[url=https://www.tinboats.net/forum/viewtopic.php?p=327583#p327583 said:


> Johny25 » Today, 11:00[/url]"]Yes elevation will have an effect on your motor and you will loose HP the higher you go. My guess is you will see an RPM drop but being you are running 6400 plus already you shouldn't have a problem. I would be interested in seeing the different readings you may get when up that high. I have heard some guys running a lower pitch prop at high altitude to compensate and keep engine in the recommended RPM range.
> I am no expert in high altitude operation but the way I understand it the air is less dense and has less oxygen so your motor should run rich. The motor is still pushing same amount of fuel with less oxygen....hence the rich mix. If you always run in high altitude I would suggest running smaller/leaner jets in the carb but be sure and change them back over when coming back to sea level as I believe you can run the risk of burning a cylinder.



Heading to higher elevation tomorrow, as far as I can find, there is no information regarding high elevation jets for this motor, tried everything, even called BPR? They won't even talk to you if the motor is less than a 2000 years model. 

Borrowed a 9 3/8" x 7pitch prop for up there, going to see how it works out with the elevation, going to be at 7500 and 9000 ft this weekend, will take some notes. 

Thanks 
Rob


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## Johny25 (Aug 28, 2013)

Be careful with that 7 pitch you could spin that motor to high. I would guess that you could turn that 10 pitch at around 6k even at those elevations. Yeah please post the info you get, will be useful info to those that run high altitude


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## therobzilla (Aug 30, 2013)

[url=https://www.tinboats.net/forum/viewtopic.php?p=327678#p327678 said:


> Johny25 » 28 Aug 2013, 08:06[/url]"]Be careful with that 7 pitch you could spin that motor to high. I would guess that you could turn that 10 pitch at around 6k even at those elevations. Yeah please post the info you get, will be useful info to those that run high altitude



OK, 

I'm up on the AZ high mountains, current elevation is 7600ft, and raining like mad I must say. 

Stated the day with the 7 pitch, as stated above the motor even at this elevation will seriously overev with the 7 pitch, RPM's not even at WOT are in the high 6000, say 6700 and that's not even WOT with speeds holding steady at 17mph. Good thing I borrowed the prop! 

Switched back to the 10 pitch, and the number are 6000 RPM's at WOT at 20 mph steady. Motor is running fine, no apparent decrease in motor operations, starts on second pull idles fine. 

Johny25 you were right on the money! 

Will check the plugs for sighs of performance when I'm done.


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## BCOWANWHEELS (Sep 23, 2013)

hhigh altitude the air gets thin and you will definatly loose hp so if I was you I,d not run wot. on my semi tk. when I went over the rockys I was tought to pull them 2 gears less to protect the engine.
bob


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## turbotodd (Sep 24, 2013)

[url=https://www.tinboats.net/forum/viewtopic.php?p=330129#p330129 said:


> BCOWANWHEELS » 22 Sep 2013, 22:23[/url]"]hhigh altitude the air gets thin and you will definatly loose hp so if I was you I,d not run wot. on my semi tk. when I went over the rockys I was tought to pull them 2 gears less to protect the engine.
> bob




It will be low on power, no doubt! But the mixture will be richer, so no worry about burning it up by going lean. It'll just be a little fatter and lazier. 

On the big diesel stuff, the turbocharger is forcing the air into the engine. Wastegated turbocharged engine is still going to make XX amount of intake pressure (boost). That being said if the turbo is already close to being out of it's peak efficiency based on shaft speed vs airflow, a little more turbo shaft speed might make it a little less efficient (heat) which can then affect power and EGT. Most modern engines will adjust just fine without fear of hurting it.


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## BCOWANWHEELS (Sep 28, 2013)

on all my semi's they had no waste gates. and blowers was as big as I could by back then offered by cummins. they made a hi-altitude blower which I bought and when used at lower elavations really put the boost out but I had to watch it close as I could burn pistons really easy pulling hard. (dont ask me how I know lol)

on the jack plate, nice job pal,I,am building me one right now very similar to your design.
regards
bob


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