View Full Version : Is it worth fixing

08-19-2008, 12:28 PM
"Its a Sears aircooled 3.5 hp outboard. Thanks to you guys I got the info on it - 1980, made by Tecumseh. The guy that sold it to me said the gas/oil mix was 16:1 - way off the information I got here that said 50:1. I talked to someone who said make it 40:1 just to be safe. The problem has been that I've been fiddling with the gas mixture screw, was running decent for a little while but hard finding the right setting.

Lately it starts and runs but will stall as soon as I increase the throttle. I don't know what I'm doing so called a boat shop and they said they don't deal with aircooled motors as people put the wrong oil in and mess them up. The motor is kind of a PITA as its only got one forward gear so your moving as soon as you get it going. Now I'm also noticing an oil leak underneath the cylinder I think where the grooves are and it goes all the way down the shaft to where the top of the "wings" (?) are.

It always starts and idles, and I wonder if its worth fixing. I paid $250 for it and I'm beginning to wonder if I got ripped off or I should work with it. Any advice appreciated,thanks..."

08-19-2008, 01:33 PM
"If your motor is 1980, it would have called for 50:1, but 40:1 is safe and won't foul plugs too badly. One thing I noticed with Eska/Sears Tecumseh aircooled outboards that I have is that the manual always calls for TC-W oil, not regular 2-Cycle chainsaw type oil. I have a service manual that states the same thing. I've never argued about it and use TCW-3 oil in them and have for years with no issues.
As for oil leaking under the cylinder, I'm not sure. There is no oil tank to leak. I'm assuming you either have a fuel leak and most of the gas is evaporating leaving the oil to drip down the motor, or you have some type of gasket leak. I have a 5 hp Tecumseh that had an issue with the head bolts coming loose and the symptoms were similar to yours. I could run it slow, but as soon as I tried to hit the throttle it lost all power. It was losing compression out the head gasket. I assume that that would be a good spot for unburnt fuel/oil to come out too, which would look like an "oil leak".
I'd start with the simple things first - check spark/clean carb/replace fuel pump element/make sure you're using proper fuel/oil, then look at some of the bigger things.
You have a high speed and idle screw on your carburetor. Turn them both in until they gently seat, and turn them out one turn. That is a good starting point. Adjust slowly with the motor running afterwards.
You can also do a compression test on it to make sure you don't have the same issue I did, or worse, worn rings etc. Sorry, I don't know what the compression should be on your motor - anybody else?
As for being ripped off, I don't know. If the motor ran good, it might be ok. Look at the price of a brand new motor in the same hp range."

08-19-2008, 02:18 PM
"Thank you for your advice. The advice on the tcw-3 goes against what I have heard but I know you know your stuff. I am using the 2 cycle chainsaw oil so maybe a change would help?

I also could only find one screw to adjust, just was outside checking it out - its got a spring on it. I did what you suggested snugged it until it sat and then backed off, started it up and already its idling much better.

Can get it up to full throttle now without stalling but its irregular at the higher idle. Maybe in water it would run better at this setting? I'd like to save it if I can but I realize that a modern motor for more money would have less to deal with (hopefully). Any other input appreciated and thanks much."

08-19-2008, 09:45 PM
"Don't run the motor out of water. It has a water pump impeller that cools the exhaust and bottom part of the cylinder. You will damage the impeller running out of water. The motor will also overheat at least a bit if the impeller is not working.
Using TCW-3 definitely goes against everything I've ever heard of with air cooled engines as well. However, my air cooled Eska manual, as well as service manual state to use TCW oil, so I do.
You might have a fixed high speed jet in your carburetor, I don't know your exact configuration.
The good news is that it sounds like your motor is responding to a simple adjustment, so you may get away with minor repairs. I'd still recommend replacing the fuel pump element in the carb, and any jets that you can. Brand new carb parts are available on eBay. I'd also put in a new spark plug. J13Y (replaced by J12YC)."

08-20-2008, 08:21 AM
"Thanks for your help, I'll take your advice."