engine noise?

[csuram99]

I have a 2003 200efi (2.5). Under different situations, i hear a squeal-like sound from the engine area. I've had others in the boat who don't hear it until i point it out, so it's not real loud. Here is what i've observed or checked:
1) noise does not occur in neutral, reverse, or low-mid rpms in drive (while chugging)
2) noise comes when i really torque the motor, like opening up to get the boat on plane
3) noise seems pretty constant when on plane, but it seems to skip, based on wave action, or turning of the boat
4) motor runs great (260 hours), good hole shot, never bogs down
5) plugs all look good, compression good
6) Lower unit oil looks good
7) Already checked alternator, belt, and belt tensioner; it's not from them

Anybody else ever experienced anything like this. I know it could be a lot of different things, but i would appreciate some advice to try and narrow it down. Thanks

[bigfishcatcher]

Check your lower unit oil - may be low!

[csuram99]

I changed the oil to look for water and metal flakes and refilled it. Everything looked good.