advice convert 2GM raw to fresh water cooling

[Northeaster]

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???

[Paul L]

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

[never monday]

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

[Northeaster]

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!

[Northeaster]

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.

[hugosalt]

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).

[never monday]

I'll work up a parts list this weekend.

[Northeaster]

NeverM - Thanks! No rush, as I will be away most of next week. I'll check back after that!

[Inlet Marine Services]

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

[Pennywhistle]

Northeaster did you ever convert your 2gm to fresh water cooling
Pennywhistle

[Northeaster]

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.

[skatun]

Hi,
Should I post this as a new topic or replying here since this topic is 6 years old?

So here are my thoughts on the topic:
Why do it?

• So I recently rebuilt my Yanmar, and there was a rather large degradation of the top due the saltwater, and two channels were almost completely clogged up!

• The motor is 99% of the time running to cold to have a good efficiency.

What to watch out for when converting:

• The exhaust manifold and exhaust will see higher temperature, make sure this is ok.

• The exhaust valves are designed small due to the fact that they are designed for running rather cold. So my idea is to add a thermometer to current setup and then run the motor on low rpm with high load(like at mooring with propeller spinning) for quite some time and record the maximum temperature.(this will be higher than max rpm because then its sucks in more cold air, and more water)
  

So my idea how to do this rebuilt:
Get a gray water filter for the saltwater in(mine doesnt have one at least..)
Get a heat exchanger:https://www.aliexpress.com/item/Heat...AbTest=ae803_4

Get a thermostat which opens around(70C?)
And a circulation pump(12V or add to the motor itself?)

Has anyone done something similar?