'97 Mercruiser 3.0 Squealing noise, not belts

[CPro]

Hey guys, As the subject says, I've got a 1997 Mercruiser 3.0 in a Sea Pro walkaround and the boat has developed a somewhat high pitched squeal. It sounds somewhat like belt squeal, but more consistent. I know it's not the belt because I disconnected the belt and ran it for a few minutes and the squeal was still there. The sound does diminish when the boat is under load (even accelerating a bit in neutral will make it go away). It sounds to me the like the noise is from the front portion of the engine...at this point I don't think it's from the rear portion. For what it's worth, this is the first year that I've kept the boat in the water. It's a pretty persistent noise and I was hoping you all might be able to help identify the source of it so I can fix it up in time to enjoy some of the good striped bass fishing we get in the fall. Thanks! Trevor

 

[Scott Danforth]

check to see if the harmonic damper is letting loose and the outer ring is walking forward against the motor mount. if so, buy a new damper

 

[Bt Doctur]

pull the drive to make sure its not a gimbal bearing squealing

 

[Mohawkmtrs]

Put a stethoscope (or screwdriver) to your ear and check the water pump, alternator, etc. for squealing (or unusual) noises.

Proceed until you locate noise.

 

[biggjimm]

My old 140 made a horrible squealing noise like that for a couple days & then it spit the front cam bearing backwards out of its journal. Surprisingly it didn't tear anything up. Of course I shut it down within seconds of it happening. I went ahead & put a new cam & lifters in it. And bearings of course.
Hopefully that's not the case with yours.

Just because it sounds like its coming from the front for sure, don't overlook checking things at the rear. Like the gimbal bearing that BT Doctur suggested.

Sounds have an uncanny way of "travelling" & fooling you. Especially on boat motors & drives it seems.

Good luck with it.
Jim.