Keel cooling almost always includes a dry stack exhaust
. If you have to install a sea water
pump to cool the exhaust, why not cool the engine
with the same water
Keel coolers certainly are reliable. The glycol engine
circulating pump (the one that pumps the glycol to and from the keel cooler
is much, much more reliable than a raw water pump
. And you may have a use for the sea water drive like a hydraulic pump or whatever.
But dry stack exhausts are bulky, require insulation
and a chimney/chase to carry the heat up and out. Soot from the exhaust often falls on the boat. So they are rarely used in recreational boats.