Merc 90 "Tower of Power" Noise

Hello,

I have an older Mercury 90 straight 6 2-stroke. I believe its called the tower of power. Not sure of the year, but its probably an early to mid 80's model i would guess. Engine runs great, it just makes a pretty bad squealing noise in neutral, forward and reverse. At higher rpm's it seems to go away, although may just not be able to hear it over the 2 stroke. I've been told it could be a water pump. Water pump is functioning fine. I'm wondering if its a bad bearing of some sort. its made the noise for a while now. I just inherited the boat so any help would be greatly appreciated.

Thanks!

Hoo-boy! Could be a bad top main bearing, a distributor bearing, or possible LU problems.

I'd get someone knowledgeable to check it out, for if it's a top bearing it could grenade the motor.

Jeff

PS: I'm thinking distributor bearing, assuming this model has one (ie; not an ADI).

Maybe a busted flex plate. That will sound like a bad top bearing. You can check it by grabbing 2 sides of the flywheel and pull/push up and down.

If you hear a "crink crink" the flex plate is busted.

Or take a large rubber mallet and strike the outer edge of the flywheel. It should have a bit of a "ring" to it.

If there's just a dead "thunk", likely the plate is cracked. You won't be able to see the cracks under the large backing washer.

If you find the plate is cracked, let us know and we can run thru the process of replacing.

Don't run it until you figure it out, you don't want the engine to grenade!

HTH.........ed

I agree it is probably a bearing... with the motor running and squealing, use 2ft length of 5/8 or 3/4 heater hose, and hold one end to your ear and use the other end to hold near the motor in various locations until you find where the squeal is is the loudest....

the squeal being heard only while in neutral tends to make me think lower main bearing....

The water pump does not have any bearings.-------When the pump is submerged it is lubricated by water and will not squeal.