90 ETLH yamaha wont accelerate over 2000 rpm

[arkboater79]

Hey, I bought a bass boat with a 90 hp yamaha 2 stroke. Took it out and ran great for maybe 2 min, then sputtered down. Seems to run good at low rpms but when throttle is applied over 2000rpms it wont accelerate and seems to run ruff like its cutting out. I replaced fuel line, cleaned carbs, changed plugs, tried choking slightly-no help,took off gas cap while running.Nothing has made a difference. I do not hear any buzzer when i start the engine or while its running which now makes me think it may be going into safe mode,if that engine even has that feature.Does anyone know if it does and if this could be my problem? The engine doesn't seem to be getting hot and this model has precision oil inj. with the reservoir mounted on motor.

 

[Woodnaut]

Re: 90 ETLH yamaha wont accelerate over 2000 rpm

Wild guess here, but might it might be starving for fuel? That is to say, fuel is making it slowy to the engine and carbs, and enough to fill up the bowls at idle (or when you squeeze the primer bulb), but not enough to sustain the engine at higher RPMs. Again, just a guess on my part, but I would look for restrictions in the fuel system such as a plugged fuel filter, anti-siphon valve, or maybe a clogged (or leaking) fuel pickup in the tank. Note that there might be some in-line strainers/filters in the fuel lines on the engine. I had an in-line filter on my F90 that was partially plugged that caused a similar situation.

 

[Profittakr]

Re: 90 ETLH yamaha wont accelerate over 2000 rpm

I agree with Woodnaut. I have a 1988 Yamaha 70 ETLG and had a similar problem a few years ago. Turns out it was a partially clogged fuel filter; the clear one mounted in the engine on the port side. We diagnosed this while running the engine and when it would not accellerate to the higher rpms; we squeezed the fuel bulb. This forced fuel through the filter to the carbs. The engine then had fuel and accelerated. A buddy of mine an I did this, constantly squeezing the fuel bulb to keep the rpms up. That told us it was a fuel problem. Since you have already cleaned out the carbs, I would check this easy fix. It is a fine nylonish screen and mine got some sort of a film on it preventing easy fuel flow. It 'looked' clean but would not pass fuel completely. $10 filter screen and good as new. Good Luck!

 

[Woodnaut]

Re: 90 ETLH yamaha wont accelerate over 2000 rpm

Yep. I did a "back flush" on mine with fuel using the primer bulb and a bunch of junk came blasting out. I knew in a second that was the problem and it was fixed just that quick. Again, this was the small in-line fuel filter on the side of the engine between the low pressure fuel pump and the VST (or in this case, the carbs).

 

[arkboater79]

Re: 90 ETLH yamaha wont accelerate over 2000 rpm

Thanks guys, It was a fuel problem with the tank itself.This forum was definitely a big help in finding my problem