"Lloyd Sumpter" wrote in message
...
On Mon, 22 Mar 2004 15:33:21 +0000, Bob wrote:

Speaking of hot water hoses and water heaters, has anyone heard of
engine
overheat problems from running engine coolant (fresh water system), a
few feet
(mayber 30 inches) above the engine block? I want to add a heater at the
helm,
but my buddy, who did the same to his similar boat, says the installer
insisted
on adding a circulation pump. Not because there wouldn't be enough
heat, but
because "the engine would overheat". This dosen't make sense to me since
the
coolant flow for the heater is parallel to the engine cooling flow. Even
if the
flow through the heater stops completely the engine should still be
properly
cooled. Any experience or ideas?

Well, if the flow stops, the engine would most certainly overheat! Where
do you
think the heat for the heater comes from?? In a FW system, the "engine
coolant"
(which is also used for the heater) cools the engine, and the raw water
cools
the engine coolant (replacing a radiator in a car).

If you wanted a Totally Independant System, you could wrap some copper or
SS
tubing round the exhaust, and use a circ pump to pump the water through
that and
up through the heater. If THAT failed, your exhaust would just get a bit
hotter.

OTOH, if the system is properly "closed", having it a few ft above the
engine
shouldn't make any difference, because what goes up comes down: the extra
energy
required to push the water UP is re-captured when the water goes DOWN.

You MIGHT have problems with airlocks in your heater, but that has nothing
to do
with circulation. You might consider expansion tank, bleed valve, etc. I'd
suggest, in fact, that THIS would be the place to add/replace the coolant,
rather than at the engine.

Lloyd Sumpter
"Far Cove" Catalina 36


Works fine. Just like your car. Block off the heater hoses and the engine
still stays cool. Parallel circuits. My forward console Jetcraft runs the
water not above the engine, but does run it about 15' each way to the heater
core.
Bill