alternator belt slipping even though tight

(jayc) · (jayc) **Join Date: Sep 2002** 04-05-2007, 3:55 AM

My alternator belt (V belt) is constatly slipping when the engine is first started. It squeals for about 30 secs then goes away unless the throttle is blipped and then it squeals again.

The belt is tight on the alternator and seems to grip the alternator pulley nicely as well as the water pump pulley but it slides over the crank pulley when I attempt to manually turn the belt.

I've cleaned the crank pulley with a rag soaked petrol to remove any grease/wd40 (its a saltwater boat so the engine bathes in wd40) but its still the same.

There was some light rust on the alternator pulley but nothing major and that just cleaned off.

Could it be the belt? It doesn't look worn or bad but maybe its just not as grippy as it should be.

(michale) · (michale) **Join Date: May 2004** 04-05-2007, 7:20 AM

if you spray wd-40 on the engine then it soaked into the belt. replace the belt and clean the pulleys with carb or brake cleaner. this should work, M.

(Message edited by michale on April 05, 2007)

(grant_west) · (grant_west) **Join Date: Jun 2005** 04-05-2007, 8:59 AM

Are you shure the belt is the correct thickness.
A 1/2 and 3/8 V-belt look very close in size. I would think if you ran a smaller belt on a larger pully it would be more prone to slipping.
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(rallyart) · (rallyart) **Join Date: Nov 2006** 04-05-2007, 10:12 AM

I've had belts start slipping that still looked good. Changing it would be the first fix that I'd try. You can buy belt dressing spray but I have not had any sustained luck with it.
Do check the size.

(guido) · (guido) **Join Date: Jul 2002** 04-05-2007, 10:39 AM

Is the belt a V-belt or is it a ribbed serpentine belt. I had an issue with my Sanger which had a Mercruiser motor. It constantly burned up belts no matter how tight it was. We never really got to the bottom of the issue, but we changed the Alternator pulley to reduce low rpm load and we eventually changed the tensioner pulley mount. The belt would still shed material and squeal lightly on occasion, but the last belt lasted better than 200 hours. The first belt was thrown at around 20 hours.

(uncc_grad) · (uncc_grad) **Join Date: Mar 2007** 04-05-2007, 11:22 AM

If the belt is new and you are sure it is tight, you can take a bar of ivory soap and let the underside of the belts run on it for a second or two and it will keep it from screaming.

(allen) · (allen) **Join Date: Apr 2005** 04-05-2007, 11:23 AM

The belt is going to slip on the crank no matter what. If you were turning the crank that meens you are turning over the motor with very little force and that meens you have bigger problems. I would try two things. Belt conditioner, or replace the belt.