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Old 09-12-2019, 17:53   #1
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yanmar alternator belt replacement

I have the new Yanmar 3YM AE which features a serpentine toothed belt no. 128990-77580.Can anyone tell me if there is an equivalent belt to the factory Yanmar belt , available at a more reasonable price
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Old 09-12-2019, 18:19   #2
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Re: yanmar alternator belt replacement

Pretty sure it is a standard 6-ribbed K/PK profile belt.

Metric check 6PK995 or use that as a crossover to various brands. 6 = number of ribs, PK=rib style, 995=length (all the way around) in mm.

You can confirm the K/PK profile by measuring the ribs from peak-to-peak, should be 3.56mm.

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[Edit] Also, note length is not an exact thing. You should have a bit of room for adjustment, so if you find one that is +/- 5mm from the stock original it will probably be OK. If you find you are always out at the furthest adjustment end then go slightly shorter, if you can barely get the belt off even at minimum adjustment then go slightly longer - added because a 990 or 1000 may be easier to find.[/edit]
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Old 09-12-2019, 18:55   #3
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Re: yanmar alternator belt replacement

Many Yanmar belts are made in Japan by Mitsuboshi. If you belt is, then the Mitsuboshi p/n is often printed on the back of the belt.

Of course, yours may be different!
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Old 09-12-2019, 21:31   #4
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Re: yanmar alternator belt replacement

Thanks guys for your replies. They have been most helpful. I have become a little tired of paying triple the price for the official factory part when it is in fact a stock item
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Old 09-12-2019, 21:51   #5
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Re: yanmar alternator belt replacement

Quote:
Originally Posted by phildy View Post
Thanks guys for your replies. They have been most helpful. I have become a little tired of paying triple the price for the official factory part when it is in fact a stock item
As are the oil filter and raw water pumps parts (impeller, bearings, seals etc).

Presumably the engine mounted fuel filter is also a stock item but it isn't one I have tried to chase down.
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Old 11-12-2019, 05:52   #6
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Re: yanmar alternator belt replacement

I wonder if a good sized hardware store turnbuckle modified with a 2" length of 1/4" rod welded at each end (to fit the pulley groove) would work to adjust the space between pulleys?
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Old 11-12-2019, 07:39   #7
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Re: yanmar alternator belt replacement

Wotname speaks with wisdom. No designer is going to design and manufacture an item when there is a stock item available. It's a fun game to find the stock items. For a Universal M25 baby diesel the throttle is available from Wetewrbeke for like $1,200, or from a heavy truck shop $150. The starter is similar - it's a Kubota off Amazon. A recent post dealt with a very fancy fuel filter - wow, there's a screw-on fuel filler on just about every outboard installation.
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Old 11-12-2019, 10:27   #8
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Re: yanmar alternator belt replacement

In my experience both Volvo and Yanmar use "standard" parts, but deliberately try to make them as non-standard as possible. Case in point is the OP's belt, both Volvo and Yanmar specify a belt that is xx5 in length, which is somewhat standard, but I've found most parts stores stock (in this size range) in increments of 10. So it may be very easy to find a 990 or a 1000, but not the "exact" 995 specified by Yanmar. Yes, they do exist, but not always in stock at the local parts place. I can't see any other reason than to make it that much more difficult to source alternative parts.
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