HELP. It fell flat at Full throttle

[flyingd]

Took the boat out for a test run and at 3500 rpm it ran fine. A couple of misses at first but then ran good. When I tried to go for full throttle it would seem to be there but then fall back and lose power. Very frustrating. I did put a new prop on it, a 17pitch, but I don't think that is over pitching this boat. It is the 120 horse mercruiser in the 18.5' chieftain.

Any ideas?

Also does anyone know the timing, point gap and spark plug gap for this boat and would it be different being that I boat at between 4 and 6 thousand feet.

Thanks

 

[CheapboatKev]

Re: HELP. It fell flat at Full throttle

Sounds more like a fuel delivery issue...you should post in the mercruiser i/o repair section for real advice.
Good luck

 

[heyyou325]

Re: HELP. It fell flat at Full throttle

I think Kev is right. Make sure there are no leaks in your fuel line, could be sucking air, not necessarily leaking fuel. fuel pump, or accelerator pump could also be culprit. Or fuel filter. full throttle sucks a lot more fuel.

 

[prelude219]

Re: HELP. It fell flat at Full throttle

I think Kev is right. Make sure there are no leaks in your fuel line, could be sucking air, not necessarily leaking fuel. fuel pump, or accelerator pump could also be culprit. Or fuel filter. full throttle sucks a lot more fuel.

I had the same problem last year..drove me nuts.. finally i tore the fuel bowl off the carb and the needle and seat was unscrewed from engine vibration and not letting the gas fill the bowl..it would idle cause it would let enough in but when the rpms were up it would run out of gas. check the carb needle and seat.