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Old 11-02-2009, 11:37   #1
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Yanmar 3YM30 Raw Water Pump Failure

I purchased my 3YM30 in 2005 in Florida. Since that time I have gone through 3 raw water pumps. The pumps are built of low quality metals and the first thing that happens is the pump shaft rusts and causes the seal to leak. Then salt water sprays all over everything and the pump bearings rust away rapidly. The pulleys all rust and cause the alternator and pump belts to chew up. My solution is in progress. I have custom made new pump shafts in 316 stainless and am buying stainless bearings, etc for the pump internals. The boat is now in Fiji. Anyone else have problems with these pumps? Anyone have any suggestions?
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Old 11-02-2009, 15:12   #2
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I have 2 of them on my cat since spring 06 working perfectly both - no leaks- and no trobles- knock on wood!- I am thinking about putting a spare on this year just in case
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Old 15-04-2009, 12:20   #3
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Complicated fix vs simple fix

I've got two 3ym30's on my cat and they are great. HOWEVER, I experienced the same pump failures on BOTH engines. My nice shiny new engines are now pretty crusty and rusted.

I got so frustrated with repeated rebuilds and outright replacements that I wired an electric pump to my port side engine. It works BUT..... Water flow doesn't increase with RPM so she's overheated a couple of times. Also, if ignition is on and engine not running, it'll pump salt water back thru exhaust into cylinder. OUCH! NOT GOOD!

I think I've got a simple fix though. I realized that the pump works fine (starboard side engine with original pump) with the drive belt pretty loose. I think I just over-tensioned the belts and the side loading wore the seals and bearings. (we're talking hand tightened here, nothing (seemingly) excessive. I thought that a slack belt would wear faster, but that's not happening.

Mike B.
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Old 27-04-2009, 20:50   #4
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Impeller pumps on yanmars are very sensitive to overtightening.......this is the main cause of failure. The side strain of the belt causes the seals to wear prematurely.

Most people have their belts way too tight.

When you tighten up via the alternator, you should be able to manually turn the alternator with you fingers...if you can't it is too tight.
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Old 27-04-2009, 21:13   #5
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Aaaah

vindication!
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Old 27-04-2009, 23:08   #6
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Quote:
Originally Posted by Chief Engineer View Post
Impeller pumps on yanmars are very sensitive to overtightening.......this is the main cause of failure. The side strain of the belt causes the seals to wear prematurely.

Most people have their belts way too tight.

When you tighten up via the alternator, you should be able to manually turn the alternator with you fingers...if you can't it is too tight.

I guess I've been lucky. I have 3GM30F Yanmars in my catamaran. I have never had any problem with the salt water pumps except the need to periodically replace the impellers over the past 14 years. I've never replaced a seal either. I must admit that the belt always seemed a bit loose, and perhaps that's why the pumps have endured.
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Old 16-11-2009, 04:44   #7
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3YM30 sea water pump

YES..we had a lot of problem with the sea water pump and the owner before me too...
when driving over 2000 rpm the alert starts because the engine gets hot. In the engine, alls systems go and okey but still this warning..
I choosed to avoid going over 2000 until i found (the engine is from 2005 and gone only 1300 hours) saltwater below the engine. The pump has totally collapsed and had to repair it. I was lucky because the greek engeneer was very competent BUT he told me that the prescribed belt (20 cm according to Yanmar) was too long!!!! He puts a 18 cm belt and since everything is okey...
WHAT IS THE ADEQUATE BELT: 18 or 20???????
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Old 13-12-2010, 10:50   #8
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I just finished Bring my 33 Morgan from Corpus Windy TX to St Pete FL and I went through 4 ! THATS RIGHT ! FOUR seals on my pump and then it failed all together about 100 off shore fron Clearwater FL
I'm looking for answers !
S/V Breezin'
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Old 13-12-2010, 11:09   #9
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See my post about the electric pump above.
I had decided last year to revert to the mechanical pump and just run the belt looser.
That worked for a while, but it just failed this month after 9 months!
I'm goin back to the external diaphragm pump and running it thru a relay actuated by the oil pressure sender (to avoid 'blowback' with stalled engine).
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Old 13-12-2010, 12:44   #10
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What does Yanmar have to say about this? And what pump # is it?

I think I would be retrofitting in a different/stronger pump with double bearings and 316 shafts. (non-magnetic)
One thing I've found from experiences was the RPM rating of the pumps can be a factor in their failure. Too many RPM's burn the seals / grooving the shafts.
Sometimes it's better to run a higher volume pump at slower RPM's, which would require a larger pump sheave.

Bronze Engine Cooling Pumps > JabscoShop - Jabsco & Rule Pumps and more - from the experts
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Old 13-12-2010, 14:20   #11
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pump

Hi,

It's a Johnson pump (in a Yanmar Box). Number is on de boat and I'm not.
Ironically, the engine with the most failures is run at low RPM most of the time for the direct drive fridge (yeah, I know....)

Not much room for a bigger pump, but good idea. I'll follow up.
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Old 13-12-2010, 14:33   #12
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Since my last post on this I had one pump go /bearings also so I bought a whole new pump $225usd and now I just replaced the other pump impeller around 1300 hours
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Old 13-12-2010, 14:51   #13
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Start with brand new pump and correct belt tension. Having read all the replies I suspect the problem is man made rather than design fault. Allthough in saying that they are not as robust as I would like considering the important job they do. Good Luck
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Old 13-12-2010, 15:00   #14
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Done that, been there.
That's exactly what I did last time.
The pump was set to the absolute minimum belt tension.
that's with the spec'ed 19m belt.

I mean, it's a good idea, but it doesn't solve the problem.
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Old 13-12-2010, 17:31   #15
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Okay then look for another cause as these are not an uncommon pump engine etc. If the failure rate was at the level you were having I am sure the pumps would have been a factory redesign. Some years ago I had a problem similar with a race engine, in this case lots of engines running but mine was the first to have the problem and it was not until I sat back and carefully pieced together what was really happening (cause of failure) that the fix which was real simple was made.
The only other idea is could there have been a faulty batch and you are just buying pumps out of that batch?
If I was you rather than just fitting another pump I would start contacting Yanmar, Johnson pumps and also take a photo of your installation and post it on the net just in case there is something you are not seeing that others might. Also the corrosion bit raised my attention (stray current etc)?
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