why do my pulleys seem bigger than they should be? (Volvo MD2020B)

alexg

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15 May 2005
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I have a problem with my recently acquired 1998 Beneteau Oceanis 281.

When fitted with the correct 9x800 v-drive belt, the belt appears to sit deeply in the jaws of the crank (touching the base of the pulleys), water pump and alternator pulleys. This in turn means that I cannot get sufficient tension on the pulley as the alternator sits right at the end of its extension arm, and I am also wearing through belts at one every 5 hrs running.

This has obviously been a historical issue as the engine bay is caked in black soot from the belts.

I have checked through everything. The pulleys are all in perfect alignments. The alternator is working fine. The start battery is tip-top. The bearings on the pulleys all appear to be fine too.

The only observation I came up with is that the pulley jaws seem to be somewhat wider than 9mm.

To test the theory, I bought a 11x800 belt and fitted it today. The belt now sits higher in the pulleys and I don't believe it is touching the bottom. I am also able to tension the alternator properly.

The engine has run about 850hrs and the alternator appears original (so not much chance of it having an mismatched pulley).

So how come my engine appears to have fatter pulleys than it is supposed to have? .... surely they cannot universally wear to that degree in so few hours?

Ideas?
 
The pulleys won't have worn. Why do you think that the 9mm, (or 10mm or 'Z' ) belt was correct?
It seems that you have pulleys for 'A' belts, 12mm or 1/2" in old money. Nothing wrong with that.
Belts should most definitely not bottom on the grooves.
 
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