Correct, the earlier 2 GM are raw water cool.
Both of my friend have 1982 Yanmar 2 GM that are raw water cool.
BTW. my raw water cool 1982, 1 GM Yanmar was used in sea water all these
years. That is from May to October of every year and winterized with
antifreeze. Now it is completely disassemble and it does not show signs of
rust damages.
The yearly replacement of the internal zinc anodes in the engine and on the
propeller shaft may have something to do with it.
The Yanmar International Rep. stated that the 1 GM raw water cool Yanmar
(6.5 HP) was introduced for use in fresh water mainly the great Lakes. The
more recent 10 GM Yanmar is designed to produce 10 HP at 3300 RPM's.
Correct me if I am wrong but I hear that this 10 GM may be on its way out to
be replaced by the new fresh water cool Yanmar 2YM15 producing 13 HP at 3400
RPM's. Other manufacturers are rating their engine at 3000 RPM. Westerbeke
are rating their 12 C, 12 HP at 3000 RPM.

"Jeff" wrote in message
...
Mic wrote:
On Tue, 06 Sep 2005 16:07:59 GMT, "Denis Marier"
wrote:


Thanks for the information.
I'll search the net for one used 2 GM.


The 2 GM is "fresh water cooled" and the 1GM is raw water cooled...

I believe both fresh and raw versions of both were built. Its true
that most 1GM's are raw, but the 2GM has many of both types. The
engine name has an "F" in it (as in 2GM20F) it is fresh water cooled,
i.e. it has a heat exchanger.