Air Cooled Outboard Overheating

[wbeaton]

I’m putting together my list of outboards to repair this winter. While making the list I was reminded of a little jet drive outboard I have. It’s a 1960’s CalJet Econo 4 with a Tecumseh powerhead and a hand crank recoil. It’s had an overheating problem since I got it. To be fair, I only tried to run it for an extended period twice. Both times it seemed to overheat after a few minutes. The first time I was running 16:1. The second time I added some more oil directly to the tank. Does anyone have one of these motors or a similar one? Is there a water pick up to cool the exhaust or something that could be plugged? I’m just looking for some thoughts to determine if this motor makes my winter list.

Wayne
Upper Canada Chapter

uccaomci.com

[Randy in Tampa]

what kind of oil are you using air cooled motors do not use TCW3? 😉

quote wbeaton:

I’m putting together my list of outboards to repair this winter. While making the list I was reminded of a little jet drive outboard I have. It’s a 1960’s CalJet Econo 4 with a Tecumseh powerhead and a hand crank recoil. It’s had an overheating problem since I got it. To be fair, I only tried to run it for an extended period twice. Both times it seemed to overheat after a few minutes. The first time I was running 16:1. The second time I added some more oil directly to the tank. Does anyone have one of these motors or a similar one? Is there a water pick up to cool the exhaust or something that could be plugged? I’m just looking for some thoughts to determine if this motor makes my winter list.

[wbeaton]

Air cooled oil. However, I’ve used TC-W oil before in a pinch with my chainsaw and weed eater without issue.

Wayne
Upper Canada Chapter

uccaomci.com

[pm-t2]

My limited experience with air-cooled two-stroke motors is that powerhead overheating is normally caused either by plugged or broken fins, or lack of shrouding to direct the air flow over the cylinder fins.

Some of those air-cooled jobbies had water-cooled exhausts, but I’m not aware of that being the case on a jet-drive type.

Didn’t see anything in this flyer about water-cooling anywhere

Hope this helps.

Best,
PM T2

PS – what are your overheat symptoms, and what spark plug are you using?

[wbeaton]

It gets extremely hot and then shuts down. It won’t restart until it cools. It doesn’t seize so it could be low compression, but I seem to remember that compression seemed ok. Of course, it’s hard to tell with the hand crank starter. It maintains spark whether hot or cold. The carb is (was) clean and adjusted for good high speed and idle on the water.

Wayne
Upper Canada Chapter

uccaomci.com

[chris-p]

Wayne,

What plug is in it?

[frankr]

I have zero experience with air cooled jet outboards. But with only one or two exceptions, all air cooled prop-driven outboards have some sort of way to pump water up to the top of the exhaust housing, where it runs back down and cools the midsection. When that system fails, the midsection gets stinking hot. Then the powerhead is like sitting on a hot stove and it overheats also. Being as a jet drive has a super water pump to drive the boat, it would only make sense to divert a small amount of that water up to cool the exhaust. But I have no idea as to whether or not the makers of your motor had "good sense" and did that.

However, bottom line is that all air cooled motors get extremely hot, compared to the water cooled ones. You can expect it to get too hot to touch. That’s just the way it is. The question then becomes why is it quitting? Since it isn’t seizing, I would explore the usual stuff, like ignition or fuel vapor lock etc.

[wbeaton]

Ok. This one just made the fourth spot on the repair list. Now I need to know what the problem is. I’ll figure it out. Plugs are J6C, which my Tecumseh literature says is correct. This is my first running air cooled outboard so I don’t have a feel for how hot "hot" should be. This is egg frying, smells like paint burning hot. Thanks for the thoughts and suggestions.

Wayne
Upper Canada Chapter

uccaomci.com

[garry-in-michigan]

First clean the cooling fins thoroughly and give them a coat of heat resistant black paint. Black paint increases heat emission efficiency. (It works on lawnmowers and automobile radiators also.) Then tap into the upper forward water plenum and run a line for cooling water into the exhaust elbow so it squirts water into the drive shaft. If the plug burns white, switch to a J4C. . . 😉

[b-morrison]

I’m not positive but… seems like there should be a bit more shrouding coming down around the cylinder, like two tabs, one on each side. Check for places where screws could have held them in place.

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