[Jilah]

Motor is a 1998 Yamaha 150 2 stroke, 6 cylinder carbureted (3) and pre-mix fuel. Has been running fine all season, I normally only get out once every two weeks or so but try to atleast start it up on the muffs and let it run a bit weekly. This past weekend the motor began cutting back at higher RPMs and would then speed up. This was pretty much a constant once I planed off and leveled out the RPMs. Engine never stalled and ran fine at idle, also started right up without any issues.

I think part of the problem is I havenÂ’t really opened the engine up this year, have been a lot of trolling and tooling around but donÂ’t think I have run it at WOT yet. Its also been run more this year at idle on the muffs than is has in the past because I havenÂ’t been getting out that much. I checked the plugs and there was some blackening so IÂ’m replacing them this weekend (put them in new this spring) along with the fuel filter and water/fuel separator. Along with that is there anything else I should change/check that might be causing my problem. IÂ’m not comfortable messing with the carbs if thatÂ’s the problem IÂ’m going to have to bring it in for service but would like to try and eliminate any other potential issues I could easily fix myself before takiing it in for service.

[esteym]

Ok, so I just had this problem with my 1994. It was a fuel problem. Look at your fuel line for kinks holes or anything else that stops/restricts/ or causes air to get fuel. Then if you take it out again and it does it have someone else drive and prime the bulb constantly. My engine would run fine then. It turned out to be a fuel pump on mine. Be sure to check your filter as well for obstruction.

Your problem sounds exactly the same. Get it fixed asap. You could do real damage to your engine.