Yanmar 3ym20 pre mature water pump failure - SailNet Community

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Old 09-30-2009
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Yanmar 3ym20 pre mature water pump failure

I have a 2 1/2 year old 3ym20 with about 400 hrs on it. After returning from a six week cruise I found the raw water pump leaking. I thought it was the hoses but it turned out to be the bearings in the pump itself. This seems to be a bit early for a water pump to give up the ghost. Any one else have this problem ?
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Old 09-30-2009
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Quote:
Originally Posted by jbrockpiano View Post
I have a 2 1/2 year old 3ym20 with about 400 hrs on it. After returning from a six week cruise I found the raw water pump leaking. I thought it was the hoses but it turned out to be the bearings in the pump itself. This seems to be a bit early for a water pump to give up the ghost. Any one else have this problem ?
Depending on where you are located, the type water and solids in the water, and also winterization techniqes, raw water pump assemblies and impellers may need service every year. If I didn't replace the impellers on mine every spring, it would surely need replacing at the most inconvenient time later that year.
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Old 10-01-2009
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Does sound like an early failure, but that happens. If you want a winter project, check out MaineSail's site for his guide on rebuilding an engine water pump.
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Old 10-01-2009
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I once had a 3GM30 and the pump bearings also failed early (300hrs). I don't think this has to do with water quality or suspended particles etc. I think it has to do with lousy bearings.
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Old 10-02-2009
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Waterpump bearings can fail pre-maturely if the belt tension is too high. Water pump seals have spring loaded lips but they have limitations if the sealing shaft is off center from the excessive load. It can cause wear on the high contact zone and partially unload the opposite side. If there are abrasives in the water, they can accelerate the wear as well. My 2GM20 has over 2,000 hrs on the original waterpump, fresh water usage only.
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Old 08-16-2010
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Reviving an old post here, but while I was researching about my own water pump problem on my 3YM20 I saw this post and would like to give an update.

My engine is around 3years old or at least as old as when they first introduced the YM series, and early this year the water pump had a small leak, then it became worse, so much so that the engine bed got flooded after an hour of cruising. After a week, the bearings ceased.

No option but to fix the pump. After Disassembly, the most important things noted were that the bearings did cease probably from saltwater from the leak.. nope they were not SS bearings, and that the water seal was in bad shape distorted, and lastly the shaft had a shallow gouge, from where I don't know!

Repair was a bit straightforward, at least the local yanmar dealer was kind enough to give a copy of the exploded illustration of the pump, including part numbers, so was able to order from them the following:

X03431760 Ball Bearing
X03431748 Ball Bearing
X02173432 O ring
X02173476 O ring (big)
X02233010 Rip Seal
X0145050 Plate

Actually the most important parts were only the 2 bearings and the Rip Seal, the others were ordered just in case, the small O ring and the plate apparently are there to provents leaks from getting to the Orings, yeah right.

Disassembly was with the help from mechanic friends using soft brass and plastic tools to prevent damaging the SS and other parts, you also need a pliers that removes ring locks.

I then sanded the gouge on the shaft, be careful to use fine grit sand paper though, i used 1000 and 1200 grit, mounting the shaft on an electric drill, be careful when using this setup, can still cause some injury.. I should know.

I also ordered a replacement impeller, with the impeller came a tube of Glycol gel that apparently is the only thing that should be used on those rubber, so I used it on the rip seal as well.

So there, if you have a 2 to 3 year old 2 or 3YM model engine, please check your water pump for leaks, and next time you order yanmar parts, you should get a rip seal as well, we don't know when your's will break.

Oh and I chatted with some engine guys in Japan, and they said, yes this is quite a common problem with the waterpump.

I still love my 3YM20, but I am not happy with how they designed the waterpump as well as whoever decided to delete the manual emergency crank feature, whoever decided to take that off the design is not a sailor at all and should keel hauled!

TTFN
Arvin
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Old 08-20-2010
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Actually, the bearing isn't the real problem. Its the water seal that leaks, thus causing problem to the bearing. Fixing is easily. You'll need some tools to press out the bearings, polish the shaft and push new bearings back in.
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Old 09-19-2010
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all the parts for these pumps are available. I rebuild them all the time. [edit]

Last edited by JohnRPollard; 09-19-2010 at 01:02 PM. Reason: no advertising in the forums, please
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