I have a 79 Mercury 402 40HP outboard which was runnign just fine this year. Last time I took it out it shifted into reverse just fine and putted along, but after I shifted into neutral then into forward I had a problem. I had to rev the throttle waaaaaay higher than I ever had to before it finally shifted into gear. Once it was in forward I had no problems running it for hours. I tried shutting it off and going into forward again and it did the same high rpm before shifting into gear. Any suggestions ?