Fuel Problem 15hp 2 stroke Yamaha

[winstonwilliams]

I have a 1991 Yamaha 15hp two stroke. I bought the motor about 6 months ago off of Craigslist for $500! The motor did not run great so I pulled the carb and cleaned it. I replaced the lower unit oil, water pump, new fuel line and gas can. I put it all back together and the motor ran like a top! It started on the first pull and ran great! Until today.. :-( Today I was going full speed and the motor just started losing power, so I reached down and pumped the bulb and the motor gained power again but I had to pump the bulb all the way home. This must be a fuel problem. but do you think it is a fuel pump or fuel filter problem? I would not think that the problem is in the carb because I just cleaned it... just curious what you think the problem is before I get into it.

Thanks

Winston

[balin206]

... did you confirm the gas tank air intake was open. I've left it closed, and had the exact same symptoms. Hope this helps.

[winstonwilliams]

Yeah that was the first thing I checked!

[winstonwilliams]

I ended up replacing the fuel diapham and it fixed the problem

[carlh]

I had a similar problem, 9.9 Yam and it turned out to be a worn/badly fitted "O" ring seal on the float bowl. The seal around the airways wasn't good, simply putting in a new seal solved the problem.