Confused about engine cooling

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mellis18

mellis18

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Nov 9, 2008
57
Hunter 31 Port San Luis, CA
I'm a little confused about the engine cooling of the 1984 Hunter 31 I just purchased. It has a Yanmar 2GM and the former owner said it was salt water cooled. However, I see a coolant reservoir with antifreeze in it. I also take off the coolant cap (what looks like a radiator cap) and there is antifreeze there also. There is a thru-hull valve and hose connection to the engine. Any help would be appreciated.
 
Ed Schenck

Ed Schenck

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Jun 2, 2004
5,802
Hunter 37-cutter, '79 41 23' 30"N 82 33' 20"W--------Huron, OH
It would surprise me if a 2GM were raw-water cooled. If it is then follow the hose from the strainer. It will go directly to the engine-mounted pump.. If fresh-water cooled the hose will go to a pump on a bracket turned by a belt. The engine-mounted pump will be only for internal engine circulation.
 
S

Steve Dion

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Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
Mellis:

I agree with Ed. I think the P.O. has a different interpertation of Sea Water Cooled. All of these engines use sea water to cool them. The difference is (as you point out) if it uses a heat exachanger or not.

If you have a coolant resevoir or not. You engine is probably a 2GM20F (fresh water/coolant resevior cooling).
 
B

Barnacle Bill

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Jun 9, 2008
1,801
- -- -Bayfield
I am looking at the service manual of a 2GM Yanmar now and there is no cooling reservoir. It is definitely sea water cooled. And it reads "Direct seas water cooling (rubber impeller water pump). I think you have a different engine than you think.
 
kloudie1

kloudie1

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Nov 6, 2006
10,104
Hunter 34 Mandeville Louisiana
The 2 GM is seawater cooled.. The 2GMF has a heat exchanger and reservoir, etc.. The 2 GM can be converted by changing a few parts. The official Yanmar shop manual has a section on exactly how to convert .. The Yanmar tag on the front of the engine should tell the story.. If it has a heat exchanger and the tag says 2GM then someone converted it, maybe even Yanmar before it went to hunter.. If it says 2GMF then that is a 2GM that was factory done with the exchanger. As far as I know, no Hunter 31's were delivered with a raw water cooled engine.
 
R

rochesterdriver

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Mar 2, 2011
53
Hunter 30 Port Bay
Mellis,

Your engine uses a heat exchanger that uses seawater to 'exchange' it's cool water temperature to 'extract' the heat from your closed loop cooling system.

The closed loop cooling system on your 2GMF (F for fresh water) contains water and antifreeze.

Your system is identical to mine.

Rich.
 
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