I was out on the water Sunday crusing along at about 35-40mph on my 98 GTI when all of a sudden the engine starts vibrating harshly and I lost thrust out of the jet pump. I let off the gas immediately and let it idle for a second and started easing back into it, at about 5 mph it was fine but anything other than that the engine would start vibrating again and you could feel the loss of thrust. Any ideas?