Engine Belt

[sailorboy1]

The belt on my Yanmar 4JH3 blew apart back in April. It was my fault I guess as that belt was 7 years old and had about 1400 hours on it. The belt was a Yanmar OEM belt and I pulled out of the channel and replaced it with my spare OEM belt.

The other day when motoring I found that the alternator wasn't charging and found that the belt was about to lose the war so replaced with my backup belt from NAPA.

That second belt wasn't really all that old and was stored in a nice dry dark locker, but it only lasted 8 months and 500 hours. This seems very short and if it were a car it would be just a few months.

So, how long are other people getting on their belts?

[RonRicco]

It seems like it is pretty common with my 3YM30s when interacting with other owners. The ones that have switched to the equivalent Gates belts are getting much more life. I have a set for both motors and are going to preemptively install them next week.

[JPA Cate]

We get years on our belts, but Jim makes quite an effort to get just the right ones, which are cogged. Inferior belts die quickly (but longer than one month).

If you tell us the known differences between the OEM belt and the NAPA (may require some research on your part), the explanation may become obvious.

If you have another NEW NAPA belt to try, it would be interesting to see how a new one lasts. Sometimes things deteriorate when stored.

You could also try a higher quality belt.

Ann

[sailorboy1]

Originally Posted by JPA Cate

If you tell us the known differences between the OEM belt and the NAPA (may require some research on your part), the explanation may become obvious.

You misunderstood. I just installed the NAPA belt. The 2 belts that failed were Yanmar OEM.

Interesting that I took the OEM over to NAPA to get another spare and ended up with a belt different from the NAPA spare I just put on. It also was more than twice the price of an OEM belt online.

A car's fan belt normally lasts years and years so I wonderwhy a boat belt would last less.

[DougR]

Sometimes belt pulleys on marine engines develop rust more readily than pulleys on automobile engines, because the boat engine pulleys sit idle for long periods of time and the car pulleys don't. This rust and the pitting that goes along with it kills the belt prematurely.

High engine room temps don't help matters either.

DougR

[Wotname]

^^ additionally there is often a much higher loading on a boat alternator belt due to battery charging - not much charging is done in a car system.

[cgebluewater]

To the question of belts suddenly wearing out quickly, I would check all pulleys to make sure they are still tight (no bolts loosening up), all pulleys still in alignment, Etc. could be an early sign of pulley coming loose, bearings in water pump or alternater going bad, Etc. If everything is perfect the belt should last a long long time.

Curious if there is a brand of belt that is widely considered the "gold" standard for belts. Always used the Yanmar OEM belt and replaced before it shows any significant wear but would interested to know who makes the best belts ?

[deluxe68]

Originally Posted by DougR

Sometimes belt pulleys on marine engines develop rust more readily than pulleys on automobile engines, because the boat engine pulleys sit idle for long periods of time and the car pulleys don't. This rust and the pitting that goes along with it kills the belt prematurely.

High engine room temps don't help matters either.

DougR

It is a good idea to use a plastic gauge such as the one in this video.

https://m.youtube.com/watch?v=87MtHNzOq3g

It may sound dumb, but I would check to ensure the belt matches the pulleys. Sometimes people install the wrong parts. Pulleys can wear out or can be out of alignment. I always liked Gates belts, the cogged belts last a bit longer under extreme heat.

[NYSail]

Originally Posted by sailorboy1

The belt on my Yanmar 4JH3 blew apart back in April. It was my fault I guess as that belt was 7 years old and had about 1400 hours on it. The belt was a Yanmar OEM belt and I pulled out of the channel and replaced it with my spare OEM belt.

The other day when motoring I found that the alternator wasn't charging and found that the belt was about to lose the war so replaced with my backup belt from NAPA.

That second belt wasn't really all that old and was stored in a nice dry dark locker, but it only lasted 8 months and 500 hours. This seems very short and if it were a car it would be just a few months.

So, how long are other people getting on their belts?

I have a 4JH4E.... second Yanmar. Do you have the front cover on? I removed my cover as it does not permit for easy checking of belts. If a belt becomes loose and is not adjusted it will wear faster. Cover off and I check engine before and after each trip.

I just installed a serpentine belt..... wonderful upgrade!
Greg

[Stu Jackson]

I've used Gates (NAPA) belts for years, long lasting,no issues. 3/8" single belts, engine info in my signature. Good luck.

[Emmalina]

Bought all sorts of spares here in Asia for backups but only ever changed one set in 10 years. I have about 7000 hours on the last ones I changed and they are fine. I see a lot of charter boats use a lot though ! I also see a lot of rusty pulleys !!!

[JPA Cate]

Sailorboy1, I must apologize, for having been out of internet range for so long, but the type of just sort of exploding you describe, would make me look for an alignment problem. It is that you experienced a step change when you replaced the old OEM belt with the new one. Something may well have become misaligned with that change, so the next belt's deterioration could be explained by that same misalignment.

Do you know how to check the alignment?

Ann

[sailorboy1]

Originally Posted by sailorboy1

So, how long are other people getting on their belts?

Thanks for the replies for me to do the basic stuff. But, above was the question

[Sailmonkey]

We were getting 500-700 hours on a Gates green stripe 3/8” cogged belt. There was a pulley width mismatch as well as a misalignment. Now with a serpentine belt, we’re up to 600 hours and no signs of trouble.

Fwiw, some 3/8” belts were too narrow for the pulleys on our Kubota engine and sat at the bottom of the groove instead of riding on the sides of the groove as intended. I’m sure this contributed to their less than stellar lifespan.

[sailorboy1]

maybe the first belt that lasted so long was the "special" belt