HELP!!! It Fell Flat On It's Face 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

 

[Leedanger]

Re: HELP!!! It Fell Flat On It's Face at Full Throttle!!!!

You are gonna have to be more specific with your question sir. Engine serial number is the most helpful. If memory serves on the 120's it is embossed on the block casting located on the starboard side.