The problem I have is that when I took the boat out on the water for the first time it was running at full throttle and all of sudden it slowed down and I could not go fast anymore. I replaced the plugs,water separator,new prop and had new ignition packs installed. The gas is fresh and the oil mixture is the same as I always used. Never had a problem with it until now. It is a 1984 90HP inline 6. Anybody have any suggestions? 