Problem with Yamaha 115 2 stroke - The Hull Truth

prolineez · 06-05-2007, 10:40 PM

I have a 2004 Yamaha 115 carb 2 stroke with about 60 hrs. on it. For about the first 20-30 minutes of use it runs good up to about 3800 rpm. When I hit the throttle at 3800 rpm, it goes up a few hundred more and then seems to hesitate. It goes to about 4200 and then suddenly jumps up to 5000, which is where it should be, for a few seconds then back down to 3600 or so. It does this very quickly, up several hundred rpm and then back down several hundred. Top rpm is only about 5000 or so. Below 3800 rpm it runs good. After 30 minutes of this it runs good. I give it some throttle and the whole rpm range is good all the way up to 5600 rpm. Once it gets going it is usually good for the whole day. This problem went on for the entire season last year, and it's driving me nuts.
I have a new fuel filter and spark plugs.

11andy11 · 06-07-2007, 07:03 PM

I had similiar problem and replace the VST fuel filter and it solved the surging.

A1 Outboard · 06-12-2007, 10:32 PM

Check fuel pressure. Also check output of high speed charge coil. Could be breaking down with heat. No VST on this motor.
Thanks Mr. J