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Old 05-03-2008, 14:13   #1
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advice convert 2GM raw to fresh water cooling

If my 25 year old Yanmar 2GM checks out OK, or needs a minor rebuild (it is out of the boat now), I may convert it from raw (salt) water cooling, to fresh water cooling.

Of course, I would have to add a 2nd water pump (build bracket for it, etc), and a heat exchanger.

Has anyone done this themselves. I can cut steel, weld, etc to fabricate brackets, etc.

I am concerned with the type of pump, and heat exchanger, that I could use.

Is there anything wrong with rigging up a new "tractor" pump, along with a heat exchanger shown below.

YANMAR TRACTOR WATER PUMP FITS 2000 2200 2500 3000 2010 - eBay (item 130203436866 end time Mar-11-08 19:12:51 PDT)



eBay Motors: Marine Diesel Engine Heat Exchanger for Perkins 4.236 (item 150221200776 end time Mar-05-08 16:29:46 PST)


I could leave the old pump providing the raw water cooling to the heat
exchanger, and use the new pump to circulate the fresh water (antifreeze).

I have a water heater, so I would like to upgrade, if feasible, and prevent any further erosion of the engine block.
Thoughts???
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Old 05-03-2008, 14:32   #2
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I don't know what this is going to cost you, but if it has worked OK for 25 years as raw water cooled, why change now? I had 3GM that was raw water cooled. It was 20 years old and running fine when I sold it. Seems like a lot of work for little gain.

Paul L
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Old 05-03-2008, 14:43   #3
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I want to know why you would reinvent the wheel of fresh water cooling on this engine. Yanmar has all the parts from other 2GM models
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Old 05-03-2008, 15:01   #4
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I am considering this, for the above mentioned benefit, of using the engine to heat the hot water tank. I did have the hot, raw water going through the water tank, but at appox 135 degrees, it only produces luke warm water. By converting to fresh water, I could put in a hotter thermostat, and therefore get hotter water out of the taps.

And although it has lasted 25 years on raw water, I f the engine is still good, I figured it wouldn't hurt to protect it a bit, with a closed cooling loop.

NeverM - It's been a while since I priced the Yanmar parts, but I bet it would be $1000 or more, for their parts vs a few hundred, if the generic parts would work.

I do appreciate the different opinions, and if it isn't worth it, I'll continue to heat water on the stove, and let the raw water cool the engine!
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Old 05-03-2008, 15:17   #5
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NeverM - If you think that the Yanmar prices are reasonable, maybe with the exception of the heat exchanger, I would consider purchasing from you, as long as you can ship to Maine. ( i live accross the border, but could pick them up there). If you have time to price things out, let me know.

Then I can determine if it is worth it, or not.
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Old 05-03-2008, 19:41   #6
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Looked into converting my 22 year old Yanmar 3 GM raw water cooled to fresh water cooled a few years ago...Yanmar dealer who would have sold me the expensive
parts told me to save my money! He has some customers with well used raw water GM motors with 25-30 years on them still going strong. But if your looking for hotter water supply... nows the time to convert, with the motor on the dining room table...so to speak.(what my father used to do).
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Old 06-03-2008, 06:40   #7
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I'll work up a parts list this weekend.
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Old 06-03-2008, 16:20   #8
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NeverM - Thanks! No rush, as I will be away most of next week. I'll check back after that!
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Old 07-03-2008, 11:07   #9
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List price from Yanmar for heat exchanger $1319.11 e-mail me and I will pdf a parts breakdown. Some marine cooler outfits offer conversion kits. inletmarineservices@comcast.net
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Old 22-11-2012, 21:04   #10
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Re: advice convert 2GM raw to fresh water cooling

Northeaster did you ever convert your 2gm to fresh water cooling
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Old 09-01-2014, 16:52   #11
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Re: advice convert 2GM raw to fresh water cooling

I know it's an old post, but may still be of interest to someone.

Let this sit for a few years and am finally going to convert to fresh water cooling.
Main reasons for doing it now
- I bought a yanmar tractor pump on ebay for another project and decided, for another $60 I would buy a 2nd pump for my sailboat to convert.
- can get a used heat exchanger large enough to pwork for about $50 fro ma friend.

Not in a rush but sometime this winter I will see how, where the new pump will mount, what size pulley is required and if I will share a belt with the alternator or run a separate one.
Have to fabricate a backing plate for the new pump, as it mounts on a flat section of the tractor engione or similar, and therefore didn't come with the a back cover.
Also will weld up a bracket to old it.

Will post when done.
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