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Grover

Misaligned alternator belt

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Just completed a short shakedown cruise with a new boat fitted with an Isuzu 42 engine and shredded the auxiliary alternator belt.  On closer inspection the alternator pulley is about 6mm out of line with the crank pulley when viewed from above, which looks like about 10 degree side deflection.  I can't believe that it's always been misaligned so it looks as though a spacer is missing between the two drive pulleys on the crank.  Does anyone know whether this is likely or have a fix for this?

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I'd check that it's mounted properly( Alternator) - if that is the case, then you can fit the required spacers to align as you say. 

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The alternator appears to be fitted properly and the alternator pulley is shimmed to ensure that the belt clears the end of the engine block.  I wonder whether a replacement  crank pulley has been fitted with insufficient stand-off from the front of the engine.

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Assuming it is also a new engine I feel your first step should be to talk to the boat builder/engine mariniser. I feel either could be at fault - the crank pulley spacer as you suggest or the wrong spacers on the engine.

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its a pre-owned boat and judging by the number of spare and used belts in the locker, this has been an on-going problem.  Does anyone know a source of pulleys as I'm hoping to find one of appropriate dimensions that will avoid the need for spacers?

 

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So not a new boat then, just new to you. I think that you need to look for the easiest way to overcome this while remaining reliable. Loads of alternator installations use spacers, in fact for 6mm on many alternators the back bracket spacer may slide enough so only a front spacer or few of washers is needed. Maybe another for the adjusting bracket. If you don't want to use washers then once you get an accurate dimension a general engineer should be able tot urn you up a spacer or if you are handy cut and file a bit of steel water pipe to length.

Edited by Tony Brooks

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1 hour ago, Grover said:

Thanks Tony, I'll have a look at the spacing options.

I don't know what alternator you have but if its a three point mounting including the adjusting bracket then the rear mounting hole usually has a sliding bush in it so you may only need to fit a spacer the the front, carefully slide the bush (they are stiff) while supporting the end bracket and maybe change the adjuster from one side of the alternator bracket to the other.

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13 hours ago, Grover said:

Just completed a short shakedown cruise with a new boat fitted with an Isuzu 42 engine and shredded the auxiliary alternator belt.  On closer inspection the alternator pulley is about 6mm out of line with the crank pulley when viewed from above, which looks like about 10 degree side deflection.  I can't believe that it's always been misaligned so it looks as though a spacer is missing between the two drive pulleys on the crank.  Does anyone know whether this is likely or have a fix for this?

If its new take it back and let them fix it  out of date now

 

Edited by ditchcrawler

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