2000 2 Stroke 115 Yamaha

I have 2000 185 Scout. I am having problems with engine running over 3900 RPM. When it goes over 3900 the throttle goes in and out and will not speed up.

Little history I bought the boat from my brother who did not run it much so gas was probably old. When I go the boat it would not idle good and not run full throttle, After replacing the parts below it idles great but will not run good or constant over 3900 RPM

1. I have ran gas down and refilled with non ethanol premium gas .
2. Installed new plugs and wires
3. Cleaned carburetor
4. Fuel Filter
5. Fuel Pump
6. I have hooked a portable tank to engine ran it and still does it
7. New gas bulb on engine gas line.


I am running out of options I have heard it could be electrical, could be a stater, could need needle values adjusted?

Did your carb cleaning include the removal of the 6 jets in both carbs (12 jets)? These jets can easily become clogged with debris, especially when old fuel has remained in fuel system. The orifice of each jet needs to be completely clear so if you hold it up to the light you can see through it. If you did not pull jets, you would experience the same engine issues when using a portable tank.

Fyi, premium gas is a waste of money. The octane recommended for your engine is 87. Filling tank with octane above 87 burns your money cause your engine will not burn the higher octane.

If you have pulled jets and cleaned, replaced filter, verified fuel pump is functioning correctly, then I'd next look at cylinder compression. This is assuming you've verified good spark after replacing the 4 plugs. You could only be firing on 3 of 4.