Single alternator belt won't stay tight

[Jeff Pospichal]

We have a 1997 454 300HP Mercruiser. We're still having trouble keeping the single belt for the alternator tight. The belts keep loosening and squealing. It's the correct belt and it's not due to a rusty pulley. We think it may be the alternator adjustment arm that keeps moving out of position.

Is it possible the hardware and or the adjustment arm itself is too weak and shifting position while under torque?

Has anyone had this same issue?

 

[bruceb58]

Re: Single alternator belt won't stay tight

Are the pulleys clean with no rust?

 

[EddiePetty]

Re: Single alternator belt won't stay tight

........The belts keep loosening and squealing.

...more than likely the product of belt vibration at speed.

If you can, run the engine through your normal routine waterborne while some one observes the 'long leg' of the belt. I'll wager at some rpm range the 'long leg' will slap (vibrate) excessively and/or the alternator will shake excessively.
The correcive action will be to install the shortest belt possible with the correct width belt and to ensure that the alternator is adequately supported. If this condition has been allowed to occur over an extended period, the threads in the mounting points of the alternator may be failing.

 

[Don S]

Re: Single alternator belt won't stay tight

MY guess rusty pulleys that keep wearing down the sides of the belt. The rust acts like sand paper. Probably have black belt dust all around the front of the engine.

 

[Kainon]

Re: Single alternator belt won't stay tight

Make sure the pivot bolt is tightened, not just the swing arm bolt. I would also suggest a Toothed Washer between the Flat washer and Slotted Arm. That would give it some bite.

 

[Jeff Pospichal]

Re: Single alternator belt won't stay tight

Hey guys, thanks for the feedback.

We knew the rusty pulley was a possibility. We've cleaned up the pulley in the past but the rust is of course a constant issue with a saltwater boat.

Is anyone aware if there is such thing as a stainless steel pulley? If so, where could we purchase one at?

Thanks in advance.