Sounds to me like you have the steering wheel turned one way or the other when you hit the gas? If that is the case, when you hit the throttle the prop is blasting your rudder all of a sudden with a tremendous amount of force(water). The rudder being turned one way or the other is catching the brunt of the force which you can hear until you straighten the wheel. Does that sound about right? No problems, just keep the wheel straight when you accelerate hard out tha hole.