"Ken Heaton" wrote in
news:HYvTf.3141$J43.2422@edtnps90:

This is a setup similar to a automotive heater. A very small water
coil (looks like a little car radiator) is in a cabinet with a fan.
It draws air from the cabin, blows it through the water coil and back
out into the cabin area. No air is drawn from the engine area. The
water coil is in the coolant line that takes the hot water from the
engine to the heat exchanger so it get the heat out of the water
before the heat exchanger gets rid of it.



http://www.rustrepair.com/app2/onlinecat.htm?r=ms&p=wi

I've got heater C in the stepvan shop in the back. 20,000 Btu is a LOT of
recovered waste heat. I can make it 90F in short order when it's 25F
outside. Take your pick. All you need is standard auto heater hose and a
shutoff valve (also available from Mill Supply on this website) to control
it and secure it in the off season.

Of course, I wouldn't recommend it for raw water cooled engines. Seawater
would eat it in short order....