Why am I shredding belts on Yanmar?

john_morris_uk said:
Charge controllers ("smart" regulators) can't produce more current than the alternator was designed to produce. This is certainly or self evidently true - but with a traditional regulator and a starter battery being up or near full charge most of the time, the belt doesn't have to transfer much power for very long. My point was (and I think you are agreeing with me) is that a 90 amp alternator charging a large house battery bank that is allowed to run down a long way, can be asked to produce near it's full output for a longer period. Actually, in practice, the alternator gets hot and self limits to a degree (if you'll pardon the pun).

However I suppose my supplementary question should have been, "Have you fitted a bigger alternator?"
Click to expand...


That makes sense.
I make a point of not having too much running (fridge in particular) when starting the engine after a period of non-running (or after a long passage normal sailing with lights/ instruments). Just taking it easy for the first 5 minutes avoids most of the furious initial re-charging / belt slip.
We have the standard Hitachi Alternator for our 4jh4AE with 3 x house batteries, 1 engine and 1 thruster battery.
There are some belts available which though nominally the right length are too narrow and sit deep in the pulleys. Ours are flush with the pulley rims.
 
0ur boat has a 110 amp Balmar alternator and smart charger as OE.

The Balmar smart charger has a 'soft start' facility. The charging lamp stays on for 30 seconds or so, until the engine has warmed up a tad, before starting the charging, which is in steps until warmed up fully.

Standard Yanmar belts would wear quickly and produce black dust and required frequent adjustment.

As others have found, and subsequently advised on here, a change to Gates belts fixed this premature wear.

For the coming season I intend to use a small bottle screw between the adjusting bolts to assist accurate tensioning. Getting a lever in to tension the unit in our aplication is not easy. As I need to remove the alternator to replace the impeller I shall modify the mounting and adjusting bolts so a small bottle screw will push the unit into the correct tension.

Worth a punt, anyway.......................................
 
john_morris_uk said:
Alternator axis out of line so pulleys not on the same axis

My favourite one that doesn't get noticed...

But could be any of the others or a combination as said.

.................................................
Click to expand...

+1 I had this problem on my secondhand engine. It took me a while to trace the cause. It was simple. The previous owner apparently reconditioned the water pump. Putting it back together, he put the washer on its axle over the pulley instead under it (or vice versa, can't remember) where it belonged. It fitted perfectly and if I didn't have a look at the drawing in the workshop manual, I wouldn't have the slightest suspicion. It made only about 1/2 mm difference, but the effect was enormous.
 
Last edited:
Yeah, belts with the teeth seems to fix it.
Also, the bracket supporting the cooling hose can get belt allowing various parts of the hose (mine), bracket and cover to make contact with the belt.
It's also possible to bolt that bracket into the wrong hole which is quite close to the right hole.
 
You must log in or register to reply here.

Share this page

Top