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Is this an issue with the belt of my 2008 3.0L MerCruiser?

J

jonolomu

New member
Please see link here for video with audio.

I'm very new to boats, and my MerCruiser inboard is making a squealing noise when in neutral or in low RPM.

Sounds like the belt to me, any guides on replacing this myself if that's the case?
 
jonolomu said:
Please see link here for video with audio.

I'm very new to boats, and my MerCruiser inboard is making a squealing noise when in neutral or in low RPM.

Sounds like the belt to me, any guides on replacing this myself if that's the case?
Click to expand...
Yeah, it's an issue. Something is very unhappy. But it is probably not a belt itself, since they don't make noises. It is something driven by a belt, either the power steering pump or the alternator. You can figure out which by removing the power steering belt (the first one that is removable) and seeing if the noise stays or goes away. Or use a stethoscope.
 
Its most likely the alternator or circulating water pump. Remove the belts and turn by hand, look for play and feel for roughness
 
head that too many times. poss causes;
a high charge rate
loose belt
BELT RIDING TOO DEEP IN ALT PULLY
BELTS SHOULD BE AT OR SLIGHTLY ABOVE THE PULLY LIP
if riding deeper theres no grip, go to a metric belt if necessary
 
Thanks for the suggestions! I used a stethoscope and the noise is defs coming from the alternator. Checked the battery and it was 12.86V without the engine running, then 13.21V with the engine running, which with some googling suggests the alternator is not doing it's job properly?

Will remove the alternator belt tomorrow and check the alternator by hand but suspect I'll just need to replace it. Seems straightforward enough to do myself.
 
13.21 would be in the normal range. It can vary anywhere from 13.0 to 14.5 and be fine. Your alternator is charging, but the front bearing has likely gone bad.

There may be an automotive electrical shop in your area, look for one that does Generators, Starters, Alternators. Getting them to repair yours is preferable usually to buying a "remanufactured" one, which is just someone else's that has been repaired and repainted.
 
When a motor first fires up the ALT output is in the 13.2 range. If the motor rpm is increased above 1000 and idled back down it normally shows 14.5
 
Ah good to know, thanks.

I've removed the alt belt and it's no longer making the noise. If I manually turn the alt I can hear the tiniest squeak in one particular point in the rotation, but its hard to imagine thats the source of the noise as it's barely audible? I got my electriic drill to rotate it at a much higher RPM I can't hear the noise over the drill, even though during operation I can hear it over the much louder engine.

...maybe that's not it and it's an issue with the belt itself? Slipping or rubbing or something? I can't see any visible issues with the belt itself.
 
The alternator spinning freely is not the same as when it is spinning with the belt running it. The pressure of the belt pulls the armature against the bearings and in turn the noise is amplified and vibrates throughout the engine making it louder. If there is no drag when spinning the alt, replace the belt and before installing the new one, clean the pulley with brake parts cleaner. If the noise is still there, change the alternator

That belt can be changed in a very short time.
 
Is the belt shiny, or dull on the surfaces that ride on the pulleys? If it's shiny, it was loose and is now glazed.

As a test, squirt a bit of water on the belt while the engine is idling or whatever speed is needed to make the noise. If it stops, relace the belt.
 
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