Squeaking or "fingers on chalkboard" sound from back of engine

[Augoose]

This is a '89 Mercruiser 4.3 w/Alpha I.

I've done several searches and have read a couple posts about squeaking sounds from the rear of the engine- seems people are pointing the finger at the gimbal bearing. Well I just had mine replaced by a well recommended shop along with a bellows kit and a lower unit shift cable about 5 weeks ago, so I don't know if the sound I'm experiencing is related to that or not.

It seems to come and go with different rpm levels and it doesn't sound like one of the belts at all. At a speed which allows the boat to plane, there is no noise. Just above that speed you can hear it, and then at WOT I think its gone again - or I just can't hear it at WOT I stuck my head down in the engine well while the wife drove the boat and it really sounds like it coming from the rear of the motor. I can't see anything obvious, but the fact that it goes and comes with the rpms makes me focus on the driveline.

The sound is almost like a violent squeak, or more like a fingernails on a chalkboard kind. Or even like a vibrating piece of hard plastic. It's not loud enough for someone up on the bow to hear, but you can just make it out from the drivers seat.

Any ideas what it might be? Temp is reading normal, oil pressure is normal, runs just fine other than the noise.
Thanks!

 

[ziggy]

Re: Squeaking or "fingers on chalkboard" sound from back of engine

the only way i know to check a gimble brg is to pull the drive and then spin the brg. by hand. it should feel like nothing. like your not spinning it. then ya'll know if it's that or not.

or

maybe, take a hearing hose with ya next time out. have the wife drive and poke around with the hearing hose. see if ya can locate the sound?

 

[Augoose]

Re: Squeaking or "fingers on chalkboard" sound from back of engine

Good suggestions, thanks. Is it common for a gimbal bearing that's on its way out to make that kind of sound?

 

[c03camson]

Re: Squeaking or "fingers on chalkboard" sound from back of engine

I think Im having the same issue with my boat (5.0mpi alpha 1 Gen2). It seems to come and go and kinda sounds like fingernails on chalkboard or in an auto when you turn the steering wheel to the stops it makes that winding noise. Havent figured it out yet but it seems to come and go and right now it isnt happening.

Some answers I got were gimbal bearing, belt, bearing on one of the engine driven pulleys, power steering, cant remember the others. Boat runs fine. Ill let you know if I ever figure the problem out

 

[cannonford57]

Re: Squeaking or "fingers on chalkboard" sound from back of engine

if your satisfied the noise is from the back that shure eliminates the belts,1 possible source is the flapper valves in the ex.horns.the other ovbious one is the gimbal bearing....a shot of grease will eliminate that one...one other could be the coupler/shaft where they come in contact...even though you said the work was done by a reputable shop,nobody said their best man did the work....not trying to impune anybodys work, just a thought....

 

[Augoose]

Re: Squeaking or "fingers on chalkboard" sound from back of engine

Great suggestions all, thank you. I've got a grease gun so I'll try that first. I'm assuming the grease fitting is easy to find?