STILL breaking belts

[jakehorton15]

1994 mercruiser 4.3lx

ive been having issues with breaking the alternator V belt for some time now. I have replaced the old alternator with a Sierra marine brand a couple years back so it is aftermarket. I have checked the alignment with a straight edge and all is good there. The bearings on the alternator and water pump all feel pretty smooth. I blasted any rust off the pulleys a year ago and sprayed with enamel so they are nice and smooth. The belts will be fine for the first half of the day and snap in the afternoon. The break is clean and straight but sometimes the belt will be missing about 4 teeth where it broke at. I have tried all different degrees of tension and no luck. I am running multiple batteries with a perko switch, not sure it that would have an effect. I’ve tried all the auto parts store brands and they all break. There is no squealing to indicate it slipping either. I have read through forums for days and am at my wits end here. Anyone have any suggestions or help?

 

[nola mike]

Any wobble in the pulleys? Alignment might be ok at top edge but not so much elsewhere.

 

[jakehorton15]

Haven’t noticed any noticeable wobble in pulleys but will pay close attention next time I run it to look at the bottom of the belt and pulleys.

 

[scoflaw]

Wrong width belt ?

 

[Bt Doctur]

Well ,if everything else has been checked and alignment is good and pullys are rust free
it must be those hungry mice

 

[jakehorton15]

I did read an old forum post about a guy who kept replacing with the belt size the original owner had on it and he switch to the oem brand and it was a touch narrower. Do you think that could be my problem as well?

 

[Bt Doctur]

A narrow belt would be more of an issue than a wide one

 

[Bt Doctur]

Could the belt be hitting or rubbing bracket, bolt, hose, etc ? post some pics

 

[zellerj]

Did this issue exist before with your old alternator? I think your issue is not tension or position in the pulley. It is more catastrophic than a chronic problem. All driven pulleys must be free to spin and not get caught up because of bad bearings etc. Something must catch and stop a pulley dead. Is your alternator charging properly? Can you put your old pulley back on? Does your power steering pump have clean fluid? Dirt in the fluid may cause it to bind because of the tight passages in the pump area. .

 

[jakehorton15]

This was not an issue before with the old alternator. When we replaced the alternator we couldn’t get a belt to last more than a couple minutes. We found the alternator bracket was bored out and allowing the alternator to sag. So when we replaced that the belts lasted much longer and quit squealing.

We added another battery at the same time as replacing the alternator so I wasn’t sure if the extra strain was causing too much heat and weakening belts or causing the alternator to seize up possibly? The power steering fluid was replaced about a year ago and looks nice and clean still.

The alternator does get very warm warm very quickly so do you think it’s likely the culprit and is seizing up when at cruising speeds due to too much heat or too much strain from the draw to charge the batteries?

it doesn’t look like anything is close enough to the belt to touch and break/cut it.

 

[hoowahfun]

This was not an issue before with the old alternator. When we replaced the alternator we couldn’t get a belt to last more than a couple minutes. We found the alternator bracket was bored out and allowing the alternator to sag. So when we replaced that the belts lasted much longer and quit squealing.

I would check all the brackets holding the alternator and the bolts as well. If one of the brackets wasn't doing it's job, the other was trying to compensate and it could have weakened or had a mounting bolt loosen up or start to shear.

 

[Scott Danforth]

with multiple batteries, did you increase the size of the alternator? if so, a 105 amp alternator should have dual v-belts. actually anything over 90 amps will need either a multi-rib belt (serpentine) or dual v-belts.

if you over-tighten, the belt will break.
if you under-tighten, the belt will slip

your comment on pretty smooth on the alternator and water pump raised an eyebrow. should be glass smooth

with the belt off, can you spin the alternator with your finger?
same with water pump, should be able to spin with just the lightest touch of a finger

does your crank pulley wobble?

 

[jakehorton15]

The brackets and bolts for the alternator were replaced when we found that issue and that seemed to fix alignment issue.

We did not increase the the size of the alternator when we added the battery. It’s juat an oem spec replacement, I believe 55amp.

The alternator

 

[jakehorton15]

Pulley spins freely and doesn’t seem to have any kind of resistance. The water pump pulley makes a little noise but I didn’t think it was anything excessive. I thought it was just the gear that moves the water through making noise. Would even the smallest amount of friction cause a belt to snap?

 

[jakehorton15]

May also be worth mentioning that once the alternator belt breaks there are no other issues the rest of the day/weekend as far as the other power steering belt is concerned. So that should eliminate any issues with the water pump pulley/bearing and power steering pulley I would think

 

[AShipShow]

If you run the motor for 10 or 15 minutes, does the belt get hot? Pretty normal for them to get a little warm but they shouldn't be hot to the touch. If its very hot, it would indicate slipping which could cause premature breakage...

 

[jakehorton15]

THe belts are warm but not too hot to hold onto or anything. They don’t seem excessively hot and there is no squealing or anything else to indicate slippage.

 

[Rick Stephens]

How about a picture of your engine from up front? Maybe someone will say: "whoa, look at that!"