In neutral I can get the engine up to the RPM limit no problem. And it sounds great. But when I put it in gear (in the water), it won't go above 2,000 rpm... I am told it may be the gas?? It's a Mercruiser 350 EFI
Give some more info. How long have you had the boat? How did it work the last time you used it? Done any recent tune ups? Ever done a compression check?
Also, what is the year/model # of the engine/drive?