raising 15hp outboard on transom using wood spacer (with pics)

[kgronseth]

I recently bought a '77 15hp Evinrude electric start motor. I have it on a 14ft modified V '68 Lund that I bought last year (see pic from last summer after I repainted it - a different motor is in the pic) . I am only getting about 6mph with the motor with myself (250lbs), battery, trolling motor, gas tank, anchor and gear. The boat also has flat floor and live well added by the previous owner. I feel like I should be getting more speed. This is my first boat so I don't have a lot of experience. I noticed today the the cavitation plate was about 1.5 inches below the bottom of the boat (back of the boat is flat, straight across.)

The motor is held on the the transom with 2 clamps and I saw that I had about 1.25 inches that I could move them up and still be clamped to the transom. I used some wood ( see attached picture) I had laying around as a spacer for the motor mount to sit on. You can see in the pic that it is still clamped onto the original transom and see marks left from the previous position of the clamps. Raising it up now puts the cavitation plate about .25 inches below the bottom of the boat.

My questions:
1. Is it ok to use the wood spacer either temporarily or permanently? If not, What would be good permanent solution?
2. Will this increase my speed? (I obviously won't be going super fast, just want to get what I can out of the motor)
3. The bow also rides high when it is just myself, will this help? ( I know I could move some things to the front, but we bring my 3 yr old daughter with sometimes and I don't her to be able to mess around with a battery/gas tank)
4. Would adding a hydrofoil the engine be beneficial (for speed and the bow being high)? (I see they are pretty cheap)


Edit to add: it is a 15" transom and a short shaft motor
Thanks!

 

[pootnic]

Re: raising 15hp outboard on transom using wood spacer (with pics)

I do the same thing,have for years although it's only as big as your 2 smaller peices of wood.
I also have my outboard attached to the boat(rope) incase it ever did let go.Never has let go and I've hit hard enough to ruin a few props and take a peice off my skeg.
Looks to have a good bite on the stern,should be fine,I'd do it.
It may not solve your problem but it should help.
Do you know what size prop you have on the outboard?
My father uses a 9.9hp evinrude on a 14' springbok(about the same style as your lund),he can get on plane with 2 adults and fishing gear.
How the weight is distributed on smaller aluminums is real crucial to get the boat to plane.
Sometimes alittle weight in the bow makes all the difference in the world.
Which trim position do you have outboard in?Close to the stern or next one out should help get the bow down abit.
Get it as light as you can,move stuff around and see if you can get it to plane by yourself.
I have know experience with hydrofoils/fins.From what I've read it's either a hate or love relationship.

 

[kgronseth]

Re: raising 15hp outboard on transom using wood spacer (with pics)

I do the same thing,have for years although it's only as big as your 2 smaller peices of wood.
I also have my outboard attached to the boat(rope) incase it ever did let go.Never has let go and I've hit hard enough to ruin a few props and take a peice off my skeg.
Looks to have a good bite on the stern,should be fine,I'd do it.
It may not solve your problem but it should help.
Do you know what size prop you have on the outboard?
My father uses a 9.9hp evinrude on a 14' springbok(about the same style as your lund),he can get on plane with 2 adults and fishing gear.
How the weight is distributed on smaller aluminums is real crucial to get the boat to plane.
Sometimes alittle weight in the bow makes all the difference in the world.
Which trim position do you have outboard in?Close to the stern or next one out should help get the bow down abit.
Get it as light as you can,move stuff around and see if you can get it to plane by yourself.
I have know experience with hydrofoils/fins.From what I've read it's either a hate or love relationship.

Thanks for the reply.

I don't know what size prop. Its just the one that was on there when I bought it. Are they usually labeled or would someone be able to tell by a pic?
The trim is in the slot closest to the stern.

 

[foodfisher]

Re: raising 15hp outboard on transom using wood spacer (with pics)

15hp isn't a big engine. A big you and fuel and gear adds to the load. I'd say that engine has it's hands full. The mock up higher transom ??? I wouldn't accelerate in reverse without a safety rope attached to this overworked engine. IMHO

 

[kgronseth]

Re: raising 15hp outboard on transom using wood spacer (with pics)

15hp isn't a big engine. A big you and fuel and gear adds to the load. I'd say that engine has it's hands full. The mock up higher transom ??? I wouldn't accelerate in reverse without a safety rope attached to this overworked engine. IMHO

It's what I've got to work with at the moment. I'll add a safety rope as the previous poster stated. Seems like others are getting a lot more speed with similar conditions, just trying see what I can do with what I have.

 

[foodfisher]

Re: raising 15hp outboard on transom using wood spacer (with pics)

Be sure the engine is running well with the right rpms at wot. Then play with trim settings.

 

[pootnic]

Re: raising 15hp outboard on transom using wood spacer (with pics)

Your prop pitch and diameter should be stamped on the prop,alot of times on a blade.
It's probably not that far off anyways,just get your boat as light as possible and see if she'll plane by yourself...work from there.
If you youtube your size outboard and boat,you find afew videos of people doing just fine with the same combo.

 

[kgronseth]

Re: raising 15hp outboard on transom using wood spacer (with pics)

Your prop pitch and diameter should be stamped on the prop,alot of times on a blade.
It's probably not that far off anyways,just get your boat as light as possible and see if she'll plane by yourself...work from there.
If you youtube your size outboard and boat,you find afew videos of people doing just fine with the same combo.

I'll check tonight and see what the prop is. Yeah I have seen posts and videos of people going a lot faster with similar setups, it seems like I should be able to get a little more out of it. The engine just had the carb cleaned and a new impellor and a tune up, so it seems to be running fine. But I have no clue about the RPM's of the motor.

I am going to try and get the boat out this week sometime and will be curious to see if just getting the cavitation plate higher will make a difference. I also ordered a Doel-Fin Hydrofoil for $30. It seems like that can help keep the bow down and I might try them out and see what kind of difference, if any, that they make.

I am hoping to get a few more people to chime in as well and let me know their thoughts on the wood spacer setup and what effect it might have. I'd rather be slower and safe than a little faster and have a dangerous setup.

 

[Chinewalker]

Re: raising 15hp outboard on transom using wood spacer (with pics)

Don't bother with the fin. Something is NOT right with your motor and the fin isn't going to help anything. That boat ought to pop up on plane with a properly set up, good-running 15. Get compression checked. Check for running on both cylinders. Do not assume that the carb cleaning and "tune up" makes your motor above suspicion.

 

[kgronseth]

Re: raising 15hp outboard on transom using wood spacer (with pics)

Don't bother with the fin. Something is NOT right with your motor and the fin isn't going to help anything. That boat ought to pop up on plane with a properly set up, good-running 15. Get compression checked. Check for running on both cylinders. Do not assume that the carb cleaning and "tune up" makes your motor above suspicion.

Thanks for the reply. I have checked the compression on my own...it was 90psi in both cylinders, which from my understanding is ok since they are about the same. Would the cavitation plate being below the bottom of the boat by 1.5 inches cause it to bog down?

 

[Chinewalker]

Re: raising 15hp outboard on transom using wood spacer (with pics)

No. Having the motor that deep might make it lose a MPH or two, but it wouldn't bog down to the point of not planing off... I've run long shaft motors on my boat just to test them and all it really does is throw a bunch of water and make the handling a little "weird" at speed.

 

[kgronseth]

Re: raising 15hp outboard on transom using wood spacer (with pics)

No. Having the motor that deep might make it lose a MPH or two, but it wouldn't bog down to the point of not planing off... I've run long shaft motors on my boat just to test them and all it really does is throw a bunch of water and make the handling a little "weird" at speed.

Well, I guess that doesn't make me feel to good about the motor then. I'll try running it with it raised on the transom a little and use that as a baseline for the speed and then start to research what may be causing the issue with the motor.

Since I bought it, it has new plugs, lower gear oil, new impellor, carb kit and new gas lines in the motor.

 

[Sea Rider]

Re: raising 15hp outboard on transom using wood spacer (with pics)

What's the boat's max rated engine for ? Probably a 15 is too poor to plane that combo. Being short shaft, and adding 1" or tad more height with wooden shims, you will have 16" or tad higher transom, which is too high for that engine. Short shaft engines works ideal with 15" max 15.5" height transoms. Remove shims, test as it is, should run better. Trim engine as to have a perpendicular engine with respect to water while boat is floating with correct weight distribution. Once correctly set.

You could play with prop pitch, buy will need to know max rpm at wot to check how much under propped could be. If water flow is not passing where should pass could experiment unwanted splashes at back transom which will slow you down. Can you post a pic of the actual engine hanging from transom.

Happy Boating

 

[kgronseth]

Re: raising 15hp outboard on transom using wood spacer (with pics)

What's the boat's max rated engine for ? Probably a 15 is too poor to plane that combo. Being short shaft, and adding 1" or tad more height with wooden shims, you will have 16" or tad higher transom, which is too high for that engine. Short shaft engines works ideal with 15" max 15.5" height transoms. Remove shims, test as it is, should run better. Trim engine as to have a perpendicular engine with respect to water while boat is floating with correct weight distribution. Once correctly set.

You could play with prop pitch, buy will need to know max rpm at wot to check how much under propped could be. If water flow is not passing where should pass could experiment unwanted splashes at back transom which will slow you down. Can you post a pic of the actual engine hanging from transom.

Happy Boating

Thanks for the reply. I'll double check tonight what the max HP is listed on the plate. I know I am less and want to say I think it was 40 or 50hp, but can't remember off the top of my head. I do remember the capacity plate was a little hard to read since it it over 40yrs old. I have been running it without the shims and the cavitation plate is about 1.5 inches below the bottom of the stern which I why I am wanting to add the shims to bring it up. I can take more pics tonight of it and post them.

I also have an original service manual for the motor and will look and see what it says about RPMs and look at the prop too. I don't have anything to measure the RPMs. Can you give me more insight into exactly what I would need and something user friendly if possible. (I'll have to do more research into them too)

Thanks!

 

[Frank Acampora]

Re: raising 15hp outboard on transom using wood spacer (with pics)

Use the wood to position the engine on the transom. Once it is clamped the wood is no longer necessary--leave it or remove it--your choice.

 

[kgronseth]

Re: raising 15hp outboard on transom using wood spacer (with pics)

Here is some more info and pics:

-Per the service manual, the full throttle operating range is from 5500 to 6500 rpm.
-The prop on the motor now is a 9.5" diameter and 10" pitch which is what the service manual says was supplied with the motor. The service manual states other propeller options are 10" diameter x 5" pitch and 9.25" diameter x 8" pitch. I haven't done any research as to how the other props might change things.
-The capacity plate states the max is 50HP and 1195lbs is the max capacity.

Any more thoughts? If someone could direct me to a entry level tachometer and some basic instructions on how to do the testing that is something I should probably try.

Thanks!

Here are a couple more pics. This is with the wood spacer still being used. I also was messing with the trim and these pics were taken with it set in the 2nd closest spot to the boat. It is raining out so the pics don't have the greatest lighting in the garage.

 

[pootnic]

Re: raising 15hp outboard on transom using wood spacer (with pics)

If your really worried about the shims(I wouldn't be);you can always bolt the outboard through your transom along with those shims.
I have a 30hp with similar shims,not bolted through the transom and biting around the same amount of transom as yours.Like I said earlier,I've hit bottom plenty of times and it hasn't moved.Make sure the clamps are tight(check em once an awhile) and it shouldn't move.I still think you should be able to plane with a good running 15hp and I can't see that boat handling a 50hp.(just my opinion)

Eating my words...handles a 50hp tiller,wow wouldn't of thought that out of that semi 14'er.Could be that you are under powered but I'd still keep trying....Good luck

 

[kgronseth]

Re: raising 15hp outboard on transom using wood spacer (with pics)

If your really worried about the shims(I wouldn't be);you can always bolt the outboard through your transom along with those shims.
I have a 30hp with similar shims,not bolted through the transom and biting around the same amount of transom as yours.Like I said earlier,I've hit bottom plenty of times and it hasn't moved.Make sure the clamps are tight(check em once an awhile) and it shouldn't move.I still think you should be able to plane with a good running 15hp and I can't see that boat handling a 50hp.(just my opinion)

Thanks pootnic. I am pretty comfortable with trying it with the shims, some others were saying there may be some other issues with the motor besides it being too low, which is why I posted the other info. Yeah I don't think I'd put 50hp on it. I am typically on small lakes so I don't need a lot of speed, I just want to get the most out of what I have. Hopefully this week I can test the boat with the motor raised and see if there is any difference in speed.

 

[foodfisher]

Re: raising 15hp outboard on transom using wood spacer (with pics)

[QUOTE=
Any more thoughts? If someone could direct me to a entry level tachometer and some basic instructions on how to do the testing that is something I should probably try.

Thanks!

Search tiny tach. Many users in iboats.

 

[Willyclay]

Re: raising 15hp outboard on transom using wood spacer (with pics)

If someone could direct me to a entry level tachometer and some basic instructions on how to do the testing that is something I should probably try. Thanks!

Here ya go:

http://www.ebay.com/itm/Inductive-TACH-HOUR-Meter-2-Stroke-Gas-Engine-New-/110857294385?_trksid=p4340.m185&_trkparms=algo%3DSIC.NPJS%26its%3DI%26itu%3DUA%26otn%3D5%26pmod%3D120763425263%26ps%3D63%26clkid%3D59961273481152406