Yanmar 3GM30F burning up Alternator Belts

[SV Windrush II]

Ok so I checked the alignment with a straightedge and all three pulleys align up perfectly and all three grooves match. The belt appears to fit into the grooves fine.

The water pump pulley and alternator spins fine and no issues with bearings.

I only started burning up belts when I replaced one while I was sailing through Micronesia. Nothing else was changed. So I'm going to order the Napa belts or something better. This is really driving me crazy, I've worked on engines all my life and never had a issue with belts. Aaaggggg

[sartorst]

If your alternator is not wired direct to a battery bank and you continue to turn the battery switch off with the engine running you will be replacing the alternator soon and can eliminate that as being the problem

[SV Windrush II]

Originally Posted by sartorst

If your alternator is not wired direct to a battery bank and you continue to turn the battery switch off with the engine running you will be replacing the alternator soon and can eliminate that as being the problem

Huh? I only flipped the switch just to Check the load on the alternator, and it is wired direct to the batteries.

I'm only trying to fix the belt problem, the alternator works just fine. Putting out 14+ volts

[Sailmonkey]

Originally Posted by SV Windrush II

Huh? I only flipped the switch just to Check the load on the alternator, and it is wired direct to the batteries.



I'm only trying to fix the belt problem, the alternator works just fine. Putting out 14+ volts

What is being said is that if the alternator runs through the battery switch before feeding the batteries, the act of disconnecting the load from the alternator while it's operating can destroy the rectifier diodes in the alternator.

However if the alt does in fact go directly to the house bank you have caused no harm.

[SV Windrush II]

Originally Posted by Sailmonkey

What is being said is that if the alternator runs through the battery switch before feeding the batteries, the act of disconnecting the load from the alternator while it's operating can destroy the rectifier diodes in the alternator.

However if the alt does in fact go directly to the house bank you have caused no harm.

Ah ok whew

[Cadence]

Originally Posted by SV Windrush II

Ok so I checked the alignment with a straightedge and all three pulleys align up perfectly and all three grooves match. The belt appears to fit into the grooves fine.

The water pump pulley and alternator spins fine and no issues with bearings.

I only started burning up belts when I replaced one while I was sailing through Micronesia. Nothing else was changed. So I'm going to order the Napa belts or something better. This is really driving me crazy, I've worked on engines all my life and never had a issue with belts. Aaaggggg

I'm not sure spinning free, not under load, is a good indicator of not having a bearing problem. JMHO

[SV Windrush II]

Originally Posted by Cadence

I'm not sure spinning free, not under load, is a good indicator of not having a bearing problem. JMHO

Good point, but when I carefully feel the shaft there is no play and feels smooth on both the alternator and the water pump.

Next I will take a stethoscope and see of I can hear anything strange while it is running.

Im looking at this belt

Super HC® XP™ Belts | Gates Corporation

[jimbunyard]

Looks gimmick heavy, but hey, it's your money.

If you have a wear problem, again, the longest lived belts are wrapped agricultural duty belts as exemplified in the illustrations below. If your belt driven charging system worked fine before, it would seem to be important to remember what has changed in the system to make it start eating belts...

[Cadence]

Originally Posted by SV Windrush II

Good point, but when I carefully feel the shaft there is no play and feels smooth on both the alternator and the water pump.

Next I will take a stethoscope and see of I can hear anything strange while it is running.

Im looking at this belt

Super HC® XP™ Belts | Gates Corporation

If all else fails! If you can beg, borrow or steal a dial indicator, with a magnetic mount, you can probably find ways to mount it, and check all your pulleys for minor wobble or run out. It would seem a better belt may only be masking the real problem. Again JMHO and SWAG

[SV Windrush II]

Originally Posted by Cadence

If all else fails! If you can beg, borrow or steal a dial indicator, with a magnetic mount, you can probably find ways to mount it, and check all your pulleys for minor wobble or run out. It would seem a better belt may only be masking the real problem. Again JMHO and SWAG

I used to have one of those in my stuff somewhere, but not sure if it made it in my boat. Yes I need to find the real problem here!

[Cheechako]

It's pretty unusual with that small alternator. I had the issue on a 3QM Yanmar, but I had a 100 amp alternator and a 3 step regulator. I absolutely could not find an alignment issue. I always had used Green Stripe belts, but found a Dayco Top Cog belt to be as good or maybe better. Tried the fabric non auto belts also.
Alignment can be very hard to figure on some engines, laying a straight edge across the pulleys is often not that feasible.
Be sure you are getting the correct thickness of belt, below 3/8" there are metrics etc, some fit down in the pulley better some ride high. Contact area is important.
It was very frustrating. I had to just put a smaller alternator on and I sold the boat.

[deluxe68]

The main killer of belts is heat. It can be caused by friction and compounded by the engine compartment temperatures. I used to work with A/C and air handler motors ranging from 1/2HP up to 100HP.

1. Make sure you have matching components. Get a set of belt/pulley gauges to make sure everything fits right. All belts do not have the same slope on the sides, same for pulleys.

2. Buy a $20 belt tension gauge and learn how to use it. Trying to tension a belt by using thumb pressure deflection is NOT how to do it. You need to determine belt type and distance between pulleys to figure out proper deflection (in pounds for a specific distance).

3. Dual belt setups are nearly impossible to tension correctly unless you buy matching belts, cut from the same band.

4. Cogged V-belts usually last longer in high temp areas or with small pulley diameters because the notches help them run cooler.

[svJasmine]

I solved it with a kit from elecromaax that uses a serpentine belt.