I just got a new pontoon with a yamaha on it and it makes a whirling type sound or a high hum noise at 1000 RPM and after that it runs great till about 3/4 throttle and the engine almost like bounces and it feels like it wont get more power out. My Dad thinks the propeller isn't big enough so its not catching the water. Can anyone help me figure out whats wrong? Please.
