Transom depth????

I have a Harris Crown 270 pontoon boat. It is a pontoon not tritoon with 25-26 in toons. It is powered by a 140 suzuki four stroke. Here is the question. At low rpms a get low prop slip.... The faster I go the higher the slip up to 30% prop slip at 5700 rpm and 24-25 miles per hour. When I watch the prop cavition plate while moving above 10 miles per hour its a mess zero clean water heading toward the prop. The question is how deep should the transom plate be??? Mine seems to be 2-3 inch max in the water with the pontoon sitting in calm water. The motor cavition plate is 2 inches below that. It I raise the motor it loses bite and over revs. Should'nt the transom be a deep as the back pontoons???? I'm calling the V-hull thing the motor mounts to the transom plate.... Thanks Nutin

Re: Transom depth????

There is a lot of turbulent water passing between the tubes so the motor needs to be as deep as possible.