Fan belt lifespan

[Storyline]

There is a single fan belt on our Nanni 46hp engine (Kubota block). Assume this powers the alternator. Knowing next to nothing about engines apart from how to change the oil I would be grateful for any advice about how often to change it to reduce any risk of breakage. Have had Storyline for 5 years now and I have never changed it. It appears in good condition and there is only a small amount of black dust where it goes round various parts.

 

[awol]

Carry a spare. Almost guarantees that whatever goes wrong won't be the fan belt!

 

[Pladdatoo]

There is a single fan belt on our Nanni 46hp engine (Kubota block). Assume this powers the alternator. Knowing next to nothing about engines apart from how to change the oil I would be grateful for any advice about how often to change it to reduce any risk of breakage. Have had Storyline for 5 years now and I have never changed it. It appears in good condition and there is only a small amount of black dust where it goes round various parts.

I would have thought ANY black dust indicates some degree of wear suggesting either/both renewal and alignment is required.
Irregardless, 5 years! I change mine yearly - it's not as though they are expensive with pattern ones from the local auto parts costing a few quid.

 

[westernman]

Mine went this year.

I have now found out that it had not been changed during my ownership (5 years), despite the engine being professionally serviced. The reason given was that the standard Yanmar belt did not fit (because of a bigger non standard alternator).

I had two spares. But both were the standard Yanmar belt which was too small........

I think changing yearly is over the top. But at 5 years I would guess you are pushing your luck too far.

No reason not to use auto belts - but might be a bit of trouble to find out the right one to use. Use a notched belt. They will take more kindly to the typical fairly tight corner around the alternator and will last longer and also not slip if the alternator is generating a heavy load.

 

[Storyline]

Thanks for the replies

Suspected I was pushing my luck so will change it.

Carry a spare. Almost guarantees that whatever goes wrong won't be the fan belt!

.....

I had two spares. But both were the standard Yanmar belt which was too small........
.....

Inherited three belts in Storyline's engine parts box. On close inspection only one fitted the engine so I suspect the other two were from the previous Mercedes engine.

 

[charles_reed]

Mine went this year.

I have now found out that it had not been changed during my ownership (5 years), despite the engine being professionally serviced. The reason given was that the standard Yanmar belt did not fit (because of a bigger non standard alternator).

I had two spares. But both were the standard Yanmar belt which was too small........

I think changing yearly is over the top. But at 5 years I would guess you are pushing your luck too far.

No reason not to use auto belts - but might be a bit of trouble to find out the right one to use. Use a notched belt. They will take more kindly to the typical fairly tight corner around the alternator and will last longer and also not slip if the alternator is generating a heavy load.

I change my belt every big service - 350 hours. I always carry a spare. You need to use notched (heavy duty) belts and tighten them until you just cannot turn the alternator pulley. Contrary to popular belief fan belts don't die just by breakage - their shoulders wear down. When a belt has sunk with it's surface below that of the pulley (usually 11mm for a 13mm belt), it's useful life is over.
Additional to spare belts for alternator and raw water pump, I carry a spare raw water-pump and, usually, an alternator. How sharp the radius round the alternator pulley might be is very much down to the size of the pulley - small pulley, high-geared alternator for high output at low r pm.
If you regularly charge a large battery bank from low or have a powerful (>120 amp) alternator you're likely to find more black dust and need to change the belt more often. Those with external "smart" controllers will also use belts (and alternators) harder.
Most alternators are designed for an operational temperature of 65-80C, the temperature in an enclosed engine box of a sailboat in the Med quite easily rises above this after 12 hours use during a summer day - apparently most flotilla mechanics reckon to replace one battery and one alternator for every flotilla cycle they have.

 

[TQA]

If you have a small capacity alternator with an automotive regulator the belt will last for years if properly tensioned.

If like me you run a 100 amp alternator with a 'smart' regulator and a single V belt your belt is working very hard and even a short run with the belt tension on the slack side will wear it out. I buy the very best grade belts I can find and am happy if they do a 100 hours.

 

[oldsaltoz]

Before replacing any belt take the time to very carefully check each pulley, it only takes a tiny rest spot to havle the life of a belt.
I you see rubber dust it will often tell you what side of the pulley has the rust (or other minor damage) or indicate the direction of misalignment, look to see if there is more dust on one side compared to the other.

A for the replacement belt, I would recommend you look for a Gates Green line replacement. They are pre tensioned and very hard wearing.

Some years ago I needed to put some huge Demag lights on a bull dozer and the alternator came with oil cooling and twin pulleys. On the first start belts spun and were tightened to point of breaking before they worked at all, then after 45 minutes one broke and other all but melted. An expensive set of matched belts was fitted and 4 hours of work they also failed.

Finally a pair Gates Green line belts were installed and lasted 4 years, this equipment was operated around the clock 7 days a week in very dusty conditions.

I have no connection with the manufacturer, but all the belts in our vehicles and on the cats twin engines and generator are Gates Green line.

Clean pulleys, good alignment and quality belts are not expensive when compared to the faffing around and commotion caused by a broken belt.

Good luck and fair winds.

 

[LadyInBed]

I don't replace belts at any fixed point, they get replaced when they run out of adjustment! (I have a 24 and 12v alternators)
I carry two spares for each alternator so when a belt is replaced I still have a spare.

 

[Storyline]

Thanks for the tip about the Gates Green line of belts. Guess we fall into the half way house category as we have a larger alternator than engine spec (ours is 80amp) and also an Adverc charger. The wind generator and careful use of the batteries mean we rarely tax the alternator but I have learnt from this thread that our belt most definitely needs changing. I will also ask one of the engineers to check everything is properly aligned.

Thanks for all the advice