Air Cooled Outboard Overheating

[billw]

Those pictures are perfect, Tubs. It shows all the fan air gets ducted to the top of the cylinder. Now, how about a picture of the Cal Jet from underneath?

Long live American manufacturing!

[oltimer]

I am "guessing/trying to remember" as per what PM T2 had said earlier about a cooling spray to the lower exhaust inside. I had a unit that was overheating with the same type of engine years ago. There was a tube that picked up water (as the unit moved forward) from the bottom to spray inside near the exhaust to cool it. The carbon at the exhaust area inside had overly built up and was closing the water spray to virtually nothing coming through. Once this was all cleaned out the engine ran hot; but never over heated to shut it down again.

[frankr]

Check the ducting as the engine was originally designed (picture borrowed from smokestack). Ducting was added as horsepower and application evolved.

screen capture freeware

[wbeaton]

For reference, here is a different model and probably newer Cal Jet photo I found on the internet. It doesn’t not have a lower shroud either. I’ll dismantle the entire motor and give everything a thorough inspection/cleaning/rebuild.

Wayne
Upper Canada Chapter

uccaomci.com

[frankr]

Notice that one does not run the exhaust down through the swivel tube. Just has a regular lawn mower muffler.

[wbeaton]

quote FrankR:

Notice that one does not run the exhaust down through the swivel tube. Just has a regular lawn mower muffler.

Yes there were quite a few small differences. It makes me think my situation isn’t unique. I imagine a good cleaning of the exhaust tube may help as others have suggested.

Wayne
Upper Canada Chapter

uccaomci.com

[dave-bernard]

check for partially blocked exhaust.

[jeff-register]

I’ve read all the posts & the one about it being carboned up sounds like the best. I bet someone used too much motor oil & it is full of carbon, mostly ring lands packed full. Next is thermorunaway.

[wbeaton]

Well, I couldn’t wait to get back into this motor. All the interest you guys expressed inspired me to put the motor in the test tank today. I tried to dismantle the lower unit and powerhead. I found that the drive shaft is seized at the crankshaft and at the jet impeller. Since I don’t have any spare parts I chose not to try and separate them. I did learn that the lower unit does not pump water up the exhaust. The rings and piston look great and the rings are nice and spongy. There was a little carbon in the exhaust, which I cleaned out. The Motor wouldn’t start so I dismantled the carb and found a little debris. The diaphragm was also a little stiff so I put a new carb kit in it. It has great spark. The motor is back up and running. It is no long running hot. It does seem to be sucking a bit of air and I’m afraid it may be coming from the crank seals. Until I find another Tecumseh based Outboard for parts I will have to live with it as is. It’s a novelty outboard that I don’t plan to run much. Thanks for all the opinions. I don’t have a good answer for the overheating. It could have been the carbon in the exhaust, the air leaning out the fuel mixture or both.

https://youtu.be/Hd47dC3bJ08

.

Wayne
Upper Canada Chapter

uccaomci.com

[frankr]

By any chance, did that carburetor have a fuel pump bladder in the flange? Sounds like it is starving for fuel. I admit, I have a pretty low opinion of that diaphragm carb design.

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