"Jeff" wrote in message

I'll be curious about the results. From what I've heard,the raw water
systems don't heat the water enough to really heat up a water tank.

This is usually true because the raw water has either already been cooled by
mixing in cold water, or because the thermostat setting is at 120F or so.
In our case (Yanmar 2QM15), at least we can get at the hot water exiting the
engine before it is mixed with cold.


As near as I can tell, the target for the hot water tank is about 160
degrees. IIRC, the PS test heated to 160, and then measured to
cooldown rate - the goal was to have hot water the morning after a run.

I am sure that this is about right, but depends on how hot the water needs
to be.

I think the tstat on the Yanmar raw water systems is set at 140, but
I've also heard 125 degrees. I don't know if that implies that the
loop you speak of is reduced to this lower temp.

I don't know what it is set at - It is not easy to measure because the water
exiting the manifold is mixed with cold water in the thermostat housing. In
the set up that I am contemplating, the thermostat will actually be setting
the water exiting the water heater coil at say 120 or 140F. The engine will
therefore run hotter than this, but probably not by much - maybe 5 deg max,
until the water in the tank is hot too.

Of course, if all you did was heat the tank to 120 degrees, that would be
a big step up
from cold - it just means that you can't count on much heat left a day
later.

True - But at least it should cool down slower because it the temperature
diff is less to start with If we get luke warm water that will be better
than ice cold. And when heading out, the water should be hot if we use shore
power at the dock. I have thought about getting a Honda 2Kw generator and
that would help when away from shore power, but I need some other
justification to sell the idea!

GBM