system components are either ordered or
fabricated separately by the boatbuilder.
There are two basic types of keel coolers:
hull-surface tanks (for metal hulls) and exter-
nal tubing. A variant of external tubing is to
run the cooling water though internal or ex-
ternal channels welded to a metal hull. When
internal, these are sometimes part of the inte-
rior structural framing of a metal boat. Note
that most of these coolers aren’t usually in
or on the keel proper, in spite of the common
termkeel cooling. (Note: Consult the pump
manufacture for high-temperature pump
vanes. Don’t use raw-water plastic impeller
pumps for a closed cooling circuit. The plas-
tic vanes will fail in the hot water.)
TANK ORSHELLKEELCOOLING On metal
boats, a flat shallow tank or pair of tanks can
be welded to the inside of the hull. Coolant
exits the engine and enters these tanks,
where it circulates in contact with the exte-
rior hull shell, dissipates the heat, and then
is piped back to the engine. These tanks will
be very warm, even hot, on the inside. You
need to prevent that heat from radiating back
into the boat by covering the inside surfaces
of the tank with insulation.PART THREE: EXHAUST SYSTEMS
Figure 8-5. Dual heat-exchanger cooling with a
separate circuit for the aftercooler (Courtesy Caterpillar, Inc.)
Figure 8-6. Basic
keel cooler
(Courtesy Perkins
Engine Co.)