# 2 stroke runs at high revs, stalls at low



## dstart1 (Sep 7, 2019)

Hello, I wonder if anyone could kindly offer some advice to an engine newbie. My recently acquired 40HP 2 stroke 2 cylinder Mariner outboard (Yamaha) 40M 6E9 (year 1992) has not had much use for a while but starts easily, ticks over just about OK at idle, but stalls when I put it into forward at low speed in the water. However, if I can get it to full throttle, it runs fine at high revs, and planes the boat happily. But then at low speed it stalls again. Spark plugs are new, fuel is new. Someone has suggested a full carb strip down, but I wanted to eliminate any simpler causes first.

Any recommended videos / resources for a carb strip down of a similar type of engine?

Thanks so much!

Daniel in Bristol England


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## Milton Fox Racing (May 27, 2014)

Instead of a rebuild you could just replace it. :cheers2:


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## Hobby Dude (Aug 7, 2019)

2-stroke, I have a couple of 2 stroke bikes in my garage, and boy let me tell you, if you aren't running super unleaded gas, and using a good two stroke oil, they will run like crap with this crappy ethynol gas they push on us consumers. Find, if you can some non-ethynol fuel and try it. I know back in the 80's all machines ran great before they put that crap in our fuel purchased by our hard earned money. Now its hard to find normal gas. Sometimes you can buy fuel stabilizers and ethynol remover fluids to add to your fuel, and they work. Go to a auto parts shop and get some Stabil fuel fixer or what ever the heck they sell over there, follow the directions and add it to your fresh fuel. You could check for water in your fuel tank, or find a clear fuel filter to check if crap is getting to your carbs. Good look, good sailing! Hobby Dude!


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## geogrubb (Jul 28, 2006)

While the engine is running spray/dribble brake parts cleaner behind the carb and along the intake and any mating surfaces if the engine changes tempo you have an air leak and can take the appropriate action. Have a good one. Geo


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## crazy mike (Aug 26, 1999)

Gas with ethanol in it makes an engine run leaner. I have an older carburated Buell that needs to be rejetted twice a year as the ethanol mix moves from the danged summer to winter blends. If it's an older engine the fuel lines will swell and disintergrate on the inside causing all sorts of chaos.


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