My 20 hp yamaha is mounted on a 22' pontoon boat on a horsepower restricted lake. Top RPM is normally around 4200. Recently it started randomly revving up to above 6000 RPM in the water with no increase in speed. I have to limp around under 3000 rpm to get back home. My first thought was that the prop was spun. I made marks on the prop, shaft, nut and split pin. These marks have not moved after experiencing the over revving many times. see the attached pic. The marks are between 10 and 11 oclock
I have also tried lowering the prop in the water to prevent cavitation and that has not prevented the over revving either. The symptoms are random. The boat has a suzuki remote paired with the yamaha motor.
Any help is appreciated.
I have also tried lowering the prop in the water to prevent cavitation and that has not prevented the over revving either. The symptoms are random. The boat has a suzuki remote paired with the yamaha motor.
Any help is appreciated.
