What the heck is this sound rite after engine starts?

[Holdnon72]

Rite after I start the boat on the hose I here this sound that last for 2 seconds then it disappears....

It sounds like if you stuck a baseball card into a turning fan blade briefly then pulled it out.

Then it just disappears....rev up the rpms and nothing its totally gone

It only happens rite after the engine starts

Any ideas?

Thanks so much