i have a 2003 292 with 6.2l's...we have a significant squeel on the port side motor. it idles fine free of noise but when you put load on the motor it squeels like crazy. almost like an old car accelerating that needs a belt change. the thing is we just replaced the belts and tightened accordingly. im gonna try belt dressing. after that not sure what else to do. im pretty sure its the belt because it sounds exactly like an old car needing a new belt. any other cause if the dressing doesnt work?

The belt could be bad maybe oil got on it or something.Dressing usually will not work on serp belts.I would take belt off and turn everything to make sure its not tight.If its ok try new belt or switch them side to side to see if the noise follows.

+1 My only other thought it that it's not adjusted right??? I think about a 1/4" play in it is what I remember..... but don't hold me to that.

ehh they are brand new belts as i mentioned. im going to re-adjust it meanwhile tryi spinning all the pulley's individually. the only pulleys that shouldnt spin are the water pump and motor driven pulleys correct?

Every thing that the belt touches should turn,the sea water pump won't spin freely but should turn.You may have a bearing in the sea water pump going.Do you see any leaking at the shaft seal? If so change the pump because if its leaking the bearings are shot plus the crank trigger is right there and does not like to be sprayed with water.

have seen on cars improper belt routing will cause loud sqeals....check routing

no leaks.

improper routing?

Good point,possible that when you changed the belt its on wrong.The groved side is running on the idler pulley where the flat side should be.If I remember correctly you had this problem before the belt was changed?

Is the noise toward the front of the eng? If it is louder at the rear could be a coupler slipping.