I never had a boat with a jet motor before. So today I went for my first run. Boy was it fun!when at full throttle she was nice and quiet. Then when I'm just in neutral, at idle, I hear like a rattle or something coming from what I think is in the shafts area between motor and jet. Not loud, just worrysome. Soon as I power it up, it's gone. Should I bee concerned? What could it be? Do jets make little more noise or should I make an appointment?