Air Cooled Outboard Overheating

[wbeaton]

That was my first thought, too, but there is nothing more I can do to increase fuel flow. It does have a fuel pump diaphragm on the bottom. I replaced the diaphragm when I rebuilt the carb. There is no way to tweak the float needle contact point like on a square body diaphragm carb so it’s as good as it gets. I figure it is a lawn mower engine after all. It wasn’t really meant to run at low speed. Besides, it doesn’t have any thrust under half throttle so it won’t get run down that low very often.

On a side note, this isn’t a very well built or designed Outboard. Everything feels cheap and looks like it would break quite easily. It also cost $4 more than an OMC 3 hp when new. It’s no surprise they failed.

Wayne
Upper Canada Chapter

uccaomci.com

[frankr]

No, that diaphragm is not what I meant. Some have a 1/4" diameter X 1/2" long (usually orange) fuel pump bladder inserted into the carb’s mounting flange. A pulse hole in the gasket aligns with the bladder.

The one you replaced acts like a float. As fuel is pulled from the chamber above it, the diaphragm moves upward, which opens the inlet needle & seat, allowing fuel to flow into the chamber. As the chamber fills, the diaphragm moves downward, closing the inlet needle & seat. Process constantly repeats. The chamber above the diaphragm must be air tight so a suction can develop to pull the diaphragm up as gas is consumed.

[wbeaton]

I see see what you are asking. There is only a reed plate behind the carb.

Wayne
Upper Canada Chapter

uccaomci.com

[westwind]

Hmmm the starving for fuel theory might be the case, rather than overheating. No clogs in the fuel system? Sometime there is a screen or filter in the tank that clogs.

[wbeaton]

I won’t rule it out, Ron, but I don’t think the carb was the original issue. It ran well before I put it up a few years ago. It’s definitely running much cooler now than before. I rebuilt the carb. It’s as clean as I can make it. I went through it a couple of times. It’s good enough for now. I’ve got more important motors to focus on.

Wayne
Upper Canada Chapter

uccaomci.com

[westwind]

This gets me thinking that I should get my Cary Jet running so we can have a race.

[wbeaton]

quote westwind:

This gets me thinking that I should get my Cary Jet running so we can have a race.

You know the first and only time I ran this motor on a boat was for a jet outboard race and I won handily! Of course, the only other competitor, a 5 hp Warren Jet, wouldn’t start. I don’t feel that diminishes my victory. A win is a win. I’ve got a perfect record. 🙂

Wayne
Upper Canada Chapter

uccaomci.com

[westwind]

The Cary Jet has a Garelli moped motor that is supposed to be about 4hp, I’m hoping I’ll have the edge in technology, if it will start. Which is probably a big if.

[Steve A W]

wbeaton
This was posted on the Smokestak forum to a post about an air cooled
jet motor similar to yours.

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Exclamation Re: Help identify Lauson outboard jetdrive?
When you adjust your carb, do not set it so the engine sings like a bee at high speed! Proper setting is to adjust for best running, after the engine is warmed up, THEN back out the fuel adjuster until the engine JUST begins to break up. If you set up too lean, it causes overheating as described in the forum posted by Steve AW. At idle, set for best running, then back out the needle 1/8 turn. Steve, if you are on that forum, please pass along the info I posted. The owner probably has it set too lean. One other thing will cause heating – bad crankshaft seals.

I am surprised that that engine has the wind up starter. Those starters were only used for a few years, due to the fact that the sudden application of the strong spring on the pawl and crankshaft often lead to 2 things. 1) the starter pawl would break out the side of the starter cup on the engine or 2) the starter would actually snap the crank, where it passed into the block! A better choice would have been the pull cord starter. They both use the same starter cup and mounting on the engine shroud. Nice looking units!

Here’s a link to the post;
https://www.smokstak.com/forum/showthread.php?t=164570

Steve A W

Member of the MOB chapter.
I live in Northwest Indiana

[wbeaton]

Thanks, Steve. I’ll keep that in mind when I test it out in the spring. The part about crank seals raised my eyebrows since I’m already a little concerned about them.

Wayne
Upper Canada Chapter

uccaomci.com

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