Yanmar belt

ST840

ST840

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My two alternator belts snapped today, luckily only 1/4 Mike from home. The spares I had didn't fit (?) 🤷🏻‍♂️.
Sea start came out and fitted a 10 x 1000 belt for me to get me limped home.
Does anybody know the exact belt I need for the 6lpa dte engine? Thanks
 
PeterBoater said:
119775-77260E but you can get much cheaper belts from a motor factor, especially a specialist belt factor such as Eriks.
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Thank you, a cheaper one was what I was hoping for. Don't suppose you know if the Yanmar one is the same as the 10 x 1000 that seastart fitted for me? The mech did say it fitted but was only a get you home belt!
 
No idea, I'm afraid. Best take the old belt to a factor. When I went to Eriks they had a fitting gauge and matched my old belt exactly, allowing for the stretch in the old belt.
 
westernman said:
Only if he has the stock alternator. Often an upgraded alternator is fitted, and the belt size is different.
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Well the 10 x 1000 fitted ok, but I'd like to find the exact measurements of the original parts. But having said that the ones I had as spare were supposed to be the correct size but aftermarket. So maybe I do have an upgraded alternator. Will any 10 x 1000 work or is it a specific tooth shape?
 
We have a Yanmar 4JH4-HTE in our motorsailer.

We had serious trouble early on in our ownership with lots of adjusting needed plus lots of black rubber dust. The boat has a 110 Amp Balmar with smart regulator with 'soft start' function.

Changing to a genuine Gates notched belt has completely fixed it. The notches on the inside run allow the belt to be tighter around the small alternator pulley. Bending to the same radius as the alternator pulley by hand, an OE Yanmar belt at almost three times the price, bunched and distorted. As the belt drives on the sides of the vee pulleys, not the bottom, distortion here caused high spots which soon wore away into dust leaving a loose belt.

The current belt on our boat is five seasons old and has not been adjusted for two seasons of mostly motorsailing with the engine at 1200-1800 RPM. It has 20mm slack in the longest run between pulleys. Visual inspection and measurement with a vernier shows it is in good condition and has lost barely 0.5mm in width.

A friend with the same boat was advised to fit the serpentine belt kit with grooved pulleys. He did so at some expense but has no better performance than us.

After the early problems with genuine Yanmar belts I purchased 5 Gates notched belts.

I still have 4 in the spares locker...................................................
 
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