i really don't know anything about boats or motors, but i recent bought a 14' fiberglass trihull and a 15 hp Mariner outboard. i can only open the motor about half throttle because anything above that and it seems as though the prop will hit air pockets and freely spin in spurts. the prop itself is just below the bottom of the boat. i know the prop hitting air pockets can't be good for the engine and i have no idea how to remedy the situation. putting around my lake is okay and all, but it would be nice to make it to my fishing spots in a timely manner. any insight would be much appreciated. thanks.