My boat has a 1997 7.4L 300Hp Mercruiser with a B1 outdrive with about 90 hours on it. A week ago this last weekend I used the boat without any problems what so ever. Engine ran good though the entire RPM range all day no matter how it was operated though I think is it running slightly rich and is due for a tune-up. I put the boat in this weekend and it started ok and as I idled out of the marina, it sounded a little funny. Sounded like it was missing. After I start to accelerate once we cleared the marina the engine started missing during the acceleration process. After about 30 secs to a minute of slowly accelerating, the engine clears up and runs like normal. Even after the engine is brought back to an idle for a few minutes or so and then I put the power back on it seems to run normal. But if I idle around for about 20-30 minutes or so and then start to accelerate the engine starts to miss again and the process starts over. It almost acts as if it is "clearing its throat" before it operates normal again. I think it might be running rich or have a sticky float. It seems strange that one weekend it was fine and the next it choked. It has been about two years since the last tune-up. Would Gum-Out or any kind of gas additive help? Thank in advance for any suggestions.
