Larry wrote:

Don W wrote in news:Xp_Rf.1452
:


Somewhere in the system should be a thermostat which prevents
new coolant from being pumped into the engine until the
coolant in the block has come up to the proper temperature.
This will work whether the coolant is an antifreeze mixture
pumped through a heat exchanger, or raw water drawn through a
water intake.

Is your thermostat possibly stuck open, or missing? Or am I
missing something here?




I think what's missing is the directly cooled engine has GOT to bypass
water around the engine/thermostat into the hot exhaust to cool it long
before that thermostat ever opens. This means his hose-to-the-exhaust has
COLD water in it before the thermostat opens to cool the exhaust (and the
hot water tank). The amount of water through a thermostat that had bypass
water flowing around it would be miniscule. Outboard motors are like this,
somewhat. The exhaust hardly gets warm, certainly never warm enough to
melt the paint on it....or to heat water in a tank.

Hmm...

You are right about the exhaust manifold cooling of course, however
there should also be a hose coming directly from the engine block
which could be used as a source of HOT water to heat the hot
water heater. Perhaps it is just a matter of which hose is
connected to the hot water heater, or possibly putting in a
new fitting to allow the hot water from the block to flow
through the heater before re-entering circulation.

I think there has got to be a way to make it work like its
supposed to--even with raw water cooling.

Also, Jeff's comment about the use of lower temp thermostats
in raw water cooled engines makes sense to me, although my
5.7L Mercruiser runs around 160F, and it has raw water cooling.
However, even 145F water should be plenty hot to heat the hot
water tank, although it might take a bit longer. I think that
Roger's problem is that he is not getting 145 degree water.

Don W.