1999 mercruiser alpha 5.0L belt problem

[jy118lfd]

The belt on this motor (standard cooling) will run fine for about 25 hours then it gets thrown off and gets shreddded. I have checked all the accessories and they are fine. If I swap on a new belt it runs true on all the pulleys. The second time this happened I checked the tension every morning before using the boat. The only thing I see is when the belt is tensioned the alternator moves some. The brackets are stamped steel and seem to not be strong enough for the belt tension. The alternator has had this little movement since new though. Has anyone come across this problem? Don?


I called a merc dealer and they said the alternator brackets were not superceeded.

 

[Don S]

Re: 1999 mercruiser alpha 5.0L belt problem

What's your SN, can't look anything up by year. After 98, it all goes by SN.
Assuming this is a serpentine belt, check for rust in any of the pulley grooves. Then check the bearings in the idlers. If you can rock the idler on the shaft when tightened down up and down or side to side, then you need to replace the idler. Shouldn't be any movement except round and round. That will push the belt sideways as it wears from the rust.

 

[jy118lfd]

Re: 1999 mercruiser alpha 5.0L belt problem

It is the serp belt. I don't have the SN now I am at work. I will post that on Wednesday when I can get down to the boat. I cleaned and repainted the pulleys this year as they were getting rusty. I also replaced the tensioner pulley as the bearing had play in it as you stated. Its funny as all the schematics show a pulley over the alternator but mine only has one idler (tensioner).