Yanmar v-belt replacement

[fairseas]

As part of routine maintenance, I decided to replace the v-belt on my 2005 Yanmar 4JH4E diesel. The old belt looked good and came off the pulleys after I
loosened the alternator bolts.

However, I couldn't get the new OEM Mitsubishi belt on. It was about 1/2 inch short to get around all three pulleys (water pump, alternator and crankshaft). Belt part numbers are the same. The only difference is the profile of the new belt which is slightly wider, 1/8 inch, and sits higher in the pulleys than the older belt which was thinner and sat deeper in the pulley groove. That makes a difference.

Even with the alternator pushed as far toward the motor as is possible, there is not enough space to get the belt over the last pulley.

Has anyone had the same problem and how was it fixed?

Thanks, L' Avel

[jeff356]

Just smoked a belt on my 3GM30F over the last weekend 20 minutes into the return trip from our weekend anchorage.

New belt was definitely tighter and would not go on without help even with the alternator adjusted all the way in. Used a flat head screwdriver on the pulley and worked the belt around until it slipped on, though not much adjustment needed after it was on but sure it will stretch alittle on first use.

Could always remove the adjuster bolt to get more travel, get the belt on and then reinstall the bolt.

[disciplefk]

I had to wrestle my new belt on a little as well. If you are doing belt replacement by yourself, I recommend this product;


https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[sailorboy1]

I have had the same issue with my 4JH3 engine. Have to really push the alternator in and the bracket tends to be tight aganist the alternator.

Of course you could have the wrong belt.

[fairseas]

Originally Posted by jeff356

Just smoked a belt on my 3GM30F over the last weekend 20 minutes into the return trip from our weekend anchorage.

New belt was definitely tighter and would not go on without help even with the alternator adjusted all the way in. Used a flat head screwdriver on the pulley and worked the belt around until it slipped on, though not much adjustment needed after it was on but sure it will stretch alittle on first use.

Could always remove the adjuster bolt to get more travel, get the belt on and then reinstall the bolt.

Thanks for all the helpful replies.

Tried the screwdriver approach. Can't get enough leverage to get the belt over the last pulley. Got the belt from the Yanmar dealer, actually didn't realize I already had a spare. All had the same Mitsubishi part number.

Now thinking of preheating it with a hairdryer. Can't be too hot for the belt, at least that's what I think.
Any other tricks out there?

[Stu Jackson]

Originally Posted by fairseas

>>>>>>>>>>>
Any other tricks out there?

Take BOTH belts into a store, and have them compare them. You say one is wider, so they ain't the same belts.


Get one that fits, then buy a few more and stop wrestling something on that is the wrong size.


I spent some time (over the years) find the right belt for my engine (doesn't matter what engine). The 7390 was too tight, the 7400 was too long, but the 7395 was just right.

[kmacdonald]

It might not have the original alternator and alternator pulley. Same goes for water pump pulley.

[Stu Jackson]

Originally Posted by kmacdonald

It might not have the original alternator and alternator pulley. Same goes for water pump pulley.

Originally Posted by fairseas

>>>>>>>>>>>>>>>>>>>>>>>>>

However, I couldn't get the new OEM Mitsubishi belt on. It was about 1/2 inch short to get around all three pulleys (water pump, alternator and crankshaft). Belt part numbers are the same. The only difference is the profile of the new belt which is slightly wider, 1/8 inch, and sits higher in the pulleys than the older belt which was thinner and sat deeper in the pulley groove. That makes a difference.

>>>>>>>>>>

Good point. And, based on the OP: the belt that was on that he took off may not have been an OEM belt, the PO could have changed it and just kept the spare. I have always (tried to) remove all old "backups" that don't fit, instead of saving them. If they didn't work yesterday, they ain't gonna work tomorrow.

And often skippers get confused about belt numbers. The "11 plus twenty two more indecipherable numbers", means little when you get the right width and profile, and then you need to know the length. I found keeping them in their cardboard sheaths helps, but then, the ONLY ones I have in spares are the right ones. There may be a translation from the long numbers, but I just found the right one and bought a few years supply, and know the width and length if I have to ever go to another store.

Based on the OP's s description, they simply can't be the same belts, regardless of the part numbers, because it's a different profile and width and length. That's one of the reasons I don't hanker with the 11+ digits anymore.

Good luck.

[CassidyNZ]

I was in the islands when the alt/water pump belt failed. Put my spare on then got a replacement from the local Yanmar agent. It was only long after I got back home that I had cause to fit the new belt and found it was too short.

The alternator had been changed, was not the same as the original. Thankfully I never needed to replace the belt at sea on the way home. I now carry 2 spares.

Another thing I experienced - when I took the adjuster bolt out to get the alt closer to the engine, one of the terminals on the alt touched on the exhaust manifold and gave an almighty flash. Luckily it never blew any diodes or caused other damage. Just be aware of that if you’re trying to get more space.

[Poldhu]

Same engine.

I have a high output alternator from Balmar so its bigger and won't give you enough clearance to push the alternator in to get the belt on. I had to remove a cooling hose as well.

True story. I am embarrassed to say I actually had to go the the hospital after tearing open my finger trying to put a new belt on. (I still have no feeling on the tip of my pointer finger) I ultimately bought three belts in half inch increments of differing sizes to get one to fit.

Next, I plan of getting a serpentine kit and go that route. $500 though.....

[fairseas]

Thanks everyone for the most enlightening information and not making me feel like a total incompetent.
The equipment is all original, alternator, water pump, etc. The original belt which was replaced by the yard, get this 8-14, still looked quite good. And it had the same Mitsubishi part number. I am stubborn and baffled why the two, unused belts I got from the Yanmar Dealer in CT. won't fit. I called and checked. It's still the same part number. The online
manual for the engine says remove the water pump pulley to replace belt, but that's a completely different matter.
I did what many of you suggested: buy a slightly larger belt at a local parts store. I did and it works. Only problem, it is obviously a generic belt and doesn't look very robust. I will look for another belt of the same size but sturdier.
Thanks again for all the input.
L' Avel
Jeanneau 40.3

[kmacdonald]

I think the OEM belts are as short as possible to limit the width of the engine. With a longer belt the alternator has to be swung further out to tighten the belt. They might be cutting it a little to short to make changes easy.

[wingssail]

Originally Posted by fairseas

Thanks for all the helpful replies.

Tried the screwdriver approach. Can't get enough leverage to get the belt over the last pulley. Got the belt from the Yanmar dealer, actually didn't realize I already had a spare. All had the same Mitsubishi part number.

Now thinking of preheating it with a hairdryer. Can't be too hot for the belt, at least that's what I think.
Any other tricks out there?

Most belts have the dimensions printed on the belt, or you can look it up based on the part number printed on the belt. Mine are metric, 12.5 (width) x 1200 (length). If the old and new belt are not the same that explains why they don't fit. Buy a different belt. I get mine, and have for decades, from auto parts stores.