Mercury 3 liter eating up alternator belts

**rdoaner** · 03-05-2021, 06:14 PM

My mercury 3 liter is eating up belts like the damn cookie monster. I've set tension correctly, and after a half hour of running, the belt is usually loose. Much longer and it gets chewed up (especially if I trim the motor up or down, as that seems to put immediate load on the alternator).

Question is, why? Below is a picture showing a straightedge flush with the top of the alternator pulley hovering above the flywheel. Is it possible the alternator is too high (or flywheel too low)? And how would I even fix such a thing?

The other picture shows that paint it peeled off of the flywheel pulley and light rust is present. It's not perfectly smooth, but it doesn't seem bad. Could this be the problem? And how would I take care of that?

**flabum1017** · 03-05-2021, 07:01 PM

That roughness from the rust in the belt groove is chewing up the belt.............

**rdoaner** · 03-05-2021, 09:45 PM

Originally Posted by flabum1017

That roughness from the rust in the belt groove is chewing up the belt.............

Funny thing is it actually doesn't feel very rough if you rub your finger around it.

From the other picture, does it look like the flywheel is too low?

**flabum1017** · 03-05-2021, 10:09 PM

Lets see a picture of the alternator pulley

**FUJIMO** · 03-05-2021, 10:22 PM

**FUJIMO** · 03-05-2021, 10:22 PM

**rdoaner** · 03-05-2021, 11:39 PM

Originally Posted by flabum1017

Lets see a picture of the alternator pulley

I'll get that tomorrow. BTW is there a replacement pulley I can get so I don't have to get a whole new alternator?

**flabum1017** · 03-06-2021, 12:06 AM

from what I remember, the top of the alt pulley is thicker, the distance between the top of the pulley and center line is more than it is on the flywheel so you might be ok with the alignment........

Click image for larger version.

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**rdoaner** · 03-06-2021, 10:42 AM

Here's the pulley. i wonder if it could be mounted upside down? Also, is there a way to get a new pulley for this alternator?

Click image for larger version.

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**big tom** · 03-06-2021, 12:57 PM

We put new belts on my twin 3.0L last summer. After @ 5 hours they had stretched so I Readjusted them. Last ride of summer turning @6000 I lost charging on one motor, when we got back to the barn I pulled the crowl and the starboard side belt had blown off, Was worn to half the original with and turned inside out!. Since it was the last time out and going to a barn I cant get into all winter to work on it(different storage plans next winter) The alternator got pulled and is going in to a rebuilder to be cleaned and be spun up for a while to see if its getting warm and??. This might be a stupid thought but what if you lay a level on the flywheel and trim the motor til its level then lay a small level on the belt??. We eye balled mine and it seems good. Dunno, Maybe i left it to loose in fear of bearing wear?. My pullies are clean and rust free so?. I just went out and looked at mine on the bench and the pulley matches your's in the pick. Thick on the inside.

**2quick4u** · 03-06-2021, 01:16 PM

I have used a laser bore sighting tool before for checking alignment. They look lie a shell casing that you chamber in a rifle. Lay it in the groove of the pulley and shine it at the opposing pulley surface. Also check your mounting holes for slop if needed you can always ream with a expandable reamer to square up the hole and use a bushing