Motor height / Losing power

[samo_ott]

I have an old Johnson 25 on a light peterborough cedar strip boat. It's new to me. After getting the engine up and running it seems there are motor/boat matching issues. It has what feels like a spun prop but I changed it with another and get the same symptoms. At around half throttle it feels like it's slipping, like a clutch slipping in a car. The engine revs more but the boat slows slightly. It looks to me like the motor is too high on the boat. The transom measured at around 17.5 inches on the diagonal, not vertical. The cav plate just above the prop is around flush with the bottom but that leaves the prop less than inch below the waterline at speed, is this a proper set up?

Also when around half throttle the bow dips a bit and starts plowing in the water creating big splashing around the front hull. The tilt pin is out all the way and I even tried some shims to tilt it more to see if it would help but it made it worse. I'm considering cutting/lowering my transom by about 1.5" but do not know if it will help. Any comments please?

p.s due to the angle of the picture it looks like the cav plate is below the bottom of the boat but it is not.

p.p.s. as you can also see the static water level (stain) is just above the water pump bulge and seems to be too high also.

p.p.p.s. I did not paint it black!

 

[tashasdaddy]

Re: Motor height / Losing power

i agree you are too high, those motors required to be deeper in the water. what is the vertical measurement. should be around 15 inches.

 

[tmcalavy]

Re: Motor height / Losing power

I agree with TD. If you want to keep that motor on that boat, you can cut the transom to lower the motor or put an extension kit on the motor. I extended a 57 Big Twin 35hp and a Johnson 18hp to fit my transom. Cost less than $150 for both...each required a leg/housing extension, longer shift connector and driveshaft. Not hard to install, but it's easier to cut the transom...if you don't mind boat surgery.

 

[marquette]

Re: Motor height / Losing power

where did you find the Peterbourgh boat? they are getting harder to find in floatable condition. what year is the boat? i know that cutting the transom will be easier than converting or finding a long shaft motor but if the boat is anywhere near original condition doing a restoration might be more fun.

 

[samo_ott]

Re: Motor height / Losing power

I found it locally up here. They are relatively common as I live 3 hours away from Peterborough where they were built.

I don' mind cutting the transom It's only wood. But it makes me wonder. If the boat is 50 years old how has it ever worked properly?

Another thing, it's model # RDEL-16. Isn't the L a long shaft? E is electric start? Thus maybe the long shaft that was converted back to short at some point? did they make long shafts in '54? I can find no documentation on it.

 

[wbeaton]

Re: Motor height / Losing power

Your experiencing ventilation. EL is an electric start long shaft, which yours is no longer. Who knows where the extention went or why it was removed. I'd start looking for an extention kit or cut the transom.

BTW, Steve, do you have a spare 18 hp carb kicking around? I have a 1958 with a damaged low speed needle and seat I need to replace.

 

[jbjennings]

Re: Motor height / Losing power

Hey Steve,
get a winch and stretch the midsection. That boat looked pretty sharp from that angle in the second photo. I got my RD-15 running nicely the night before last with just 1 coil, 2 spark plug wires, cleaned points and a carb cleaning. I ran it in the barrel without changing the impeller and it pumped but not very good. when I took off the lower unit to replace it, there was only 2 fins complete and only 1 that was any good. Luckily I found the 4 broken blade pieces. I've got to wait for a darned tiller handle to test it. I believe my lower unit might actually not leak.
Make sure you take a pic of it running when you hack off your transom. Are you going to glass it after cutting or what? Your prop looked nice.
How about a paint job?? Send it to me and I'll paint it up for you!
I'm thinking a red bottom to the water line and then stained wood with a clear varnish finish on the rest. Then an original green color with Peter's decals for the motor. Get on that right away! I want RESULTS!
Later,
JBJ

 

[samo_ott]

Re: Motor height / Losing power

Well I cut off 2" of the transom today and it certainly helped out. I get much better acceleration and no slippage / minimal ventilation but I still have problems with the bow plowing down in the water. As soon as the engine powers up the bow drops and I have to drop speed. Seems weird if the boat has been doing this for 50 years??? Any ideas?

p.s. Jason, you had 2 blades left on your impeller? Then mine was a tad better. I had 3 blades left! Those damn 50 year old impellers... Didn't they build them to last! And did your coils look as bad as these? what's with the crappy old parts anyway!

 

[jbjennings]

Re: Motor height / Losing power

Hey Steve,
yeah, those evinrude/johnson engineers were definitely slackers when it comes to building stuff to last. Those coils do look suspect. Are you thinking of replacing them or just using a little tape on the insulation?

Actually, it's sometimes nice to see those because you know that motor wasn't used for a WHILE!!!!!
I would think you could raise the motor up a notch or two and it would lift that bow up a little but I'm sure you've tried that. If not, is the bottom hooked on the last foot or two of the stern? Other than that, I don't know how to solve the problem. More weight in the back maybe??
Hope you figure it out...
JBJ

 

[jbjennings]

Re: Motor height / Losing power

Steve,
I just looked at your pic again and that setup looks to me like the steering wheel is just too darned far forward. Seems like it would run much better if the drivers seat was about 2 feet farther back. I think it would look sharp if more of the bow were enclosed, too. I guess that's out of the question, though. I really think that might be the problem---all the weight is in the bow of the boat.
Just an idea,
JBJ

 

[samo_ott]

Re: Motor height / Losing power

Tried a little tape and dipping em in epoxy but no go! So I had to replace em... Just like these darned impeller vanes... they wouldn't glue back on so I had to replace it also!

HEY! The last couple of feet on the bottom is hooked up, or bent in, it looks like from the rollers. You might have pegged it. Would that do it? How the heck would I fix that?

And as for the wheel too far forward I thought of that also and sat in the back seat and held the wheel (long arms!) and the same thing. I also tried me back by the engine (230 lbs) and a light buddy (~160 lbs) driving and the same thing.

And the engine is noisy (!) don't really want to sit any closer to it. (What dummy would want a tiller on a big twin! But it does run nice. Idles right down and I did no carb work on it at all.

 

[tashasdaddy]

Re: Motor height / Losing power

i hate to put fiberglass on a wood boat, but that may be your best alternative. inorder to feather out that hook.

 

[wbeaton]

Re: Motor height / Losing power

Try moving the trim pin out another notch or two if you can. The hook may be causing you some trouble. Depends how big and deep it is.

Loud? If its too loud, you're too old! lol You should try some sound deadening. If I ever get my 1954 Big Twin on a boat I'm going to try the spray foam in a heavy garbage bag trick.

 

[samo_ott]

Re: Motor height / Losing power

Don't worry, the pin is all the way out and I even tried some shims on the back of the transom to increase the angle even more but to no avail.

TD, is the hook the problem? I had never considered it. And as the old wooden tub leaks anyway, I have no problem putting some fibreglass on it if it will solve the problem. Is it a known symptom of my problem as I have never heard of it before.

 

[wbeaton]

Re: Motor height / Losing power

Post a pic of the bottom. A big hook will act like a trim tab and push the bow down.

 

[samo_ott]

Re: Motor height / Losing power

It's in the water and I don't have an underwater camera!

 

[mickjetblue]

Re: Motor height / Losing power

Excuse me, but I'd like to find out what the old garbage trick with the spray
foam is all about to decrease noise. I'm old, but never heard of it.

 

[jbjennings]

Re: Motor height / Losing power

Steve,
Have you figured it out yet??


Mick: I've never done it but the way it was described to me was to take a stout garbage bag and put it on the powerhead and tie it good. then put your cowl on and spray some of that expanding foam stuff through one of the holes in the cowl and it will stick to the cowl---and hopefully not to your powerhead. After it sets up, you take the cowl off, then the bag, and when you remount the cowl you've got yourself some nice sound insulation. Voila?!
I may have some important details wrong, so don't try it until someone really tells you how.
JBJ

 

[tashasdaddy]

Re: Motor height / Losing power

sure sounds like a wives tale. the foam would conform to the block and linkage, could be a real PITA to get off. then how would the linkage move.

 

[samo_ott]

Re: Motor height / Losing power

Jason, where did you hear that? It would also lead to a hot running engine I'd think. I thought you liked the nice loud big twins?

and nope, the boat is the same. Assuming it's the hook underneath, I'll need to pull the boat and work on it... sigh... Yesterday I was puttering around at half throttle...

btw, we live many miles from the ramp so it takes effort and coordination to pull the boat when it's sitting at our dock.