I bought my ski last year and have only been able to ride it a few time. Whenever I'm out on the water the ski makes a weird sound when it is at idle, but as soon as you hit the gas the sound goes away. It sounds like the engine is rumbling back and forth, but honestly I have no idea what it could possibly be. The guy I bought it from said it might be a gas knock, but that was not the case. Does anyone have any ideas what is going on??