Pontoon Boat Motor Cavitation. Water disturbance from the pontoons can also cause it on some toons. First it can physically damage the propeller.
Secondly it causes those vibrations which makes your ride less comfortable. All it takes is a little wave action or loading heavy and the problem gets worse. Your engine looks a.
A similar but quite separate issue is ventilation which takes place when air is introduced to water around or to the water flow fed to a propeller.
They keep water down at your prop and intake improving water pressure. Water disturbance from the pontoons can also cause it on some toons. The propmotor setup seems to be good. More importantly the optimal outboard length prevents cavitation.
