Runs like a striped ass ape on muffs but won't accelerate above 1200 rpm in the lake. Have checked compression, spark, float level, vacuum leaks. It is a 1988 merc black max 200 2 stroke. I am in big bear altitude is about 6500' already have high altitude jets prop is a 19 pitch, fuel lines and tanks are new. Please help. Sorry the video won't upload but it runs great on the muffs. It spits and sputters then dies on acceleration above 1200 but will plow around for as long as you like and restart perfectly 1200 or below.