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Diesel This is a forum dedicated to diesel engines and their applicable accessories.

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Old 09-02-2010
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pre mature belt wear

I have a 2007 Yanmar 3ym20. last year at about 350 engine hours the raw water pump failed and sprayed saltwater on the pulleys of the engine. Although I rinsed everything off with fresh water the damage was done and rust appeared. Now over the last 70 engine hours I've had to replace three belts. The alternator pulley and the fresh water pump pulley are smooth but the main drive pulley has some corrosion that is difficult to remove. The tension on the belt is to the factory specs of 10mm deflection.
How can I get the belt from wearing ? Do I need to replace the drive pulley ?
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Old 09-02-2010
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cardiacpaul is a jewel in the rough cardiacpaul is a jewel in the rough cardiacpaul is a jewel in the rough
The short answer is "that depends"
How does the belt "blow"...
Check for misalignment between the centers of the driving and driven pulley surfaces. If thats ok, then, assume you're going to need a new pully... however if you're in a consistent salt spray type of area, I would consider taking the pulley to a machine shop and having them cut one out of aluminum.
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Old 09-02-2010
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To add to cardiacpaul's advice, if you decide to get a custom pulley made out of aluminum, first check for a pulley blank at an industrial supplier. My guess is Yanmar used a standard size pulley. You may even find one with the same hub for mating to the shaft. If not, then you can get one with a blank hub that can be custom machined for much less money than making one from scratch.

Last edited by nickmerc; 08-18-2011 at 06:29 AM.
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Old 09-03-2010
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Try CLR. Soak it in that and then repaint the pully.
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Old 09-03-2010
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Yanmar 'pressed steel' pulleys are notorious for developing roughness due to rusting. Suggest you carefully look at the FWC pump sheeve and determine if that is the (usual) culprit. If so, they are relatively cheap to replace.

The crankshaft sheeve can be 'dressed' back to smooth by a machinist - but you need to be careful so that the vee profile doesnt become 'too deep' so that the 'bottom' of the vee belt comes in contact with the 'base' of the vee groove.

To prevent sheeve roughness on Yanmars, best is to spray on some 'Boeshield' onto the sheeve vee surfaces when laying up the boat for long term.
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