Alt. belts break under load

[demeanor]

I have twin 1996 Volvo 5.0 F.I. Fords. They seem to break alt. belts under load. I might break one in one weekend or both at the same time. Alt. pulleys turn freely,no rust or burs and they are in line with pulley on crank. Belt adjustments are correct about 1/2".I have had this boat for two seasons and the problem just started in the begining of this season. I have replaced belts about 6 or 7 times. I am using Volvo Penta belts as replacements. Which is the correct part number. Any ideas?

 

[Haut Medoc]

Re: Alt. belts break under load

This question has Don S written all over it......
Post your serial #'s if possible.......
Put "Volvo" in your header....
He will get back when he sees it.....
It ain't right, you should be able to hundreds of hours on a belt....JK

 

[xtraham]

Re: Alt. belts break under load

did you have any worked performed on the engines prior to this starting ?

 

[Don S]

Re: Alt. belts break under load

I don't have a clue what does it. Are ALL the pulleys clean and free of rust? Are ALL the belts tight?
I doubt they just suddenly break in half with no marks. Something is contacting them while it's running. What part of the belts goes first, top, sides, bottom?
I would start watching them very carefully and see where the problems starts showing up You may have to go out for a day with someone else running the boat, and just keep watching while it runs, maybe shut it off and inspect them every once in a while.

 

[demeanor]

Re: Alt. belts break under load

did you have any worked performed on the engines prior to this starting ?

No, Just basic Tune up etc. Started after about first month of use this season.

 

[demeanor]

Re: Alt. belts break under load

did you have any worked performed on the engines prior to this starting ?

No, Just basic Tune up etc. Started after about first month of use this season.

Don S.,
All belts are tight and pulleys are clean. One might break in a hour or may break after three days of use. They seem to break more often under sudden throtle movement. Would serial numbers help?

 

[Don S]

Re: Alt. belts break under load

Don't need serial numbers for this problem, it's still going to take watching and seeing what is contacting them. Like I said before, I doubt the are just a clean break, most likely they start fraying and show damage somewhere on the belt before they actually break.

 

[Haut Medoc]

Re: Alt. belts break under load

Does the inside of the motor cover show any signs of contact/wear?

 

[demeanor]

Re: Alt. belts break under load

Does the inside of the motor cover show any signs of contact/wear?

Ther are no signs of hitting or rubbing on anything. They are freying before breaking. You don't even hear them break, you see them when the hatch is raised.

 

[bomar76]

Re: Alt. belts break under load

Sure you aren't buying belts designed for Fractional Horsepower applications? Look the same, will shred under a real load in no time flat.

 

[xtraham]

Re: Alt. belts break under load

only thing I can think of that you have not checked is to look for bracket problems ie: loose, cracks, missing supports, etc.

 

[DHPMARINE]

Re: Alt. belts break under load

I don't have the answer either,but I would look at the crank pulleys.See if they wobble when the motors are running.

A far guess,for twins, but possible.

DHP

 

[seahorse5]

Re: Alt. belts break under load

I have twin 1996 Volvo 5.0 F.I. Fords. They seem to break alt. belts under load. I might break one in one weekend or both at the same time. Alt. pulleys turn freely,no rust or burs and they are in line with pulley on crank. Belt adjustments are correct about 1/2".

The Ford motors have more alternator belt problems because of the mounting location. On a Chevy, the alternator is on the "pulling" side of the belt and on a Ford it is on the "pushing" side because it is installed on the opposite side of the engine.

OMC had problems like this with their Fords, and the EFI models with highter amperage draws and more powerful alternators added to the problem.

Make sure that you are using Volvo or Cobra OEM belts and that they are set new to 1/4" deflection, and then readjusted after 30 minutes running time. The factory manual says 10 minutes. Belt tension has to be checked often on the Fords, usually every 10 hours.

This is assuming that the pulleys are free from rust and are in perfect alignment. Aftermarket belts usually are not a strong or as long lasting as the factory furnished belts..

 

[sailsmanship]

Re: Alt. belts break under load

I had a boat that drove me crazy for three years doing the same thing. I used OEM belts,automotive belts,industrial belts, severe duty industrial belts, special high temp resistant belts, you name it, I tried it all... They all kept breaking.. Finally solved it... Turns out what I was doing was duplicating an error from the previous owner. The OEM belt that I was replacing and duplicating in different brand and styles was the wrong one. When I finally ordered an OEM one by just giving the motor info I never had a problem again. It was different from the OEM belt that the previous owner had put on. It rode lower in pully. Like yours, all of the other wrong ones showed no telltale wear patterns or marks.
Might not be the same problem, but when you said " do you know the correct part #, I assume you have been replacing them by duplicating them like I was... Just a thought......

 

[Don S]

Re: Alt. belts break under load

This from the original post,

I am using Volvo Penta belts as replacements. Which is the correct part number. Any ideas?

I took this as meaning he was using Volvo belts and it was the correct part number. But, he was wondering if anyone had any other ideas.

To mr. demeanor, if you post your full model number or serial number, I could verify that you have the right belt. When you say you have a 96 Volvo, you may have a 96 BOAT, but that doesn't make the engine and drive package a 96. Years don't mean much in the newer engines, like they did in the 70's and 80's. Too many accesories on the engines change. (almost daily)