My son took the boat out yesterday (21' w/5.7L engine and Alpha One outdrive), he calls and says that the rpm's dropped to 3200 rpm while trying to plane and then it fell flat on it's face and wouldn't move. He noticed that the prop would spin below 1000 rpm and was able to troll to the dock, anything above 1000 rpm the boat wouldn't move. I did some reading in the SELOC manual and about the only idea I got was a coupler on the back of the engine that the drivshaft slides into. If I put the boat in gear on dry land the prop won't spin so i'm assuming the outdrive is ok. Anyone had experience with kind of problem? If it turns out to be a coupler, how tough of a job is it to replace? John..................