My Mercruiser 454 Magnum (Alpha One, '87 Formula 242-SS) runs OK from a cold condition, but after a long run when brought back to idle, it won't go up above about 1200 rpm until it cools off -- or something. Throttling up, it feels like half the cylinders aren't firing (like 180 degrees of the distributor suddenly isn't working, not bang-miss-bang-miss), causing major vibration, and no throttle position will get it above this speed. Sometimes I can push through it to 1500rpm and up and it will go and be OK. But often I just have to idle and wait 5 or 10 minutes before I can get moving again.
At first I thought it was weeds, but backing up (which usually clears them: this is in Lake Michigan) didn't fix this, while waiting did. It also feels like it lost a prop blade, or more precisely half of the prop blades, which is a neat trick with a 3-bladed prop. They're all there, in fair condition.
Any ideas I should tell my mechanic? Unlike some of the real gear-heads I read in here, I just work on the boat by writing checks. But it's hard when he can't see the problem in his yard and I don't want to pay him by the hour to go out long enough to make it happen.
At first I thought it was weeds, but backing up (which usually clears them: this is in Lake Michigan) didn't fix this, while waiting did. It also feels like it lost a prop blade, or more precisely half of the prop blades, which is a neat trick with a 3-bladed prop. They're all there, in fair condition.
Any ideas I should tell my mechanic? Unlike some of the real gear-heads I read in here, I just work on the boat by writing checks. But it's hard when he can't see the problem in his yard and I don't want to pay him by the hour to go out long enough to make it happen.
