Westerbeke 6.5KW - COOLING System

COOLING SYSTEM
Description
Westerbeke mar ine generators are equipped wi th fresh water cooling.
Transfer of heat from engine fresh water to sea water is accomplished
by a heat exchanger, similar in function to an automotive radiator.
Sea water flows through the tubes of the heat exchanger while fresh
water flows around the tubes. The sea water and fresh water never mix
with the result that the cooling water passages in the engine stay
clean.
Fresh Water Circuit
Heat rej ected dur ing combustion, as well as heat developed by fr ic-
tion, is absorbed by the fresh water, whose flow is created by a fresh
water circulating pump. The fresh water flows from the engine through"
a fresh water cooled exhaust manifold, a heat exchanger and returns to
the suction side of the fresh water circulating pump. When starting a
cold engine, most of the external flow to the heat exchanger is pre-
vented by the closed thermostat. Some amount of bypass is maintained
to prevent overheating in the exhaust manifold. As the engine warms
up, the thermostat begins to open up allowing full flow of engine
fresh water through the external cooling system.
Sea Water Circuit
The sea water flow is created by a posi ti ve displacement neoprene
impeller pump. Normally the pump draws sea water directly from the
ocean via the sea cock and sea water strainer. Sea water then flows
directly from the discharge of the sea water pump to the heat
exchanger sea water inlet. After passing through the tubes of the
heat exchanger, the sea water enters a water injected, wet exhaust
system, the most popular type of exhaust system in use. In the case
of larger engines, the sea water flow is divided prior to entering the
exhaust systems so that a portion is used to cool the exhaust system.
Full sea water flow would create unnecessary exhaust back pressure.
Sea Water Pump
The sea water pump is self priming and positive displacement. It is a
rotary pump with a non-ferrous housing and a neoprene impeller. The
impeller has flexible vanes which wipe against a curved cam plate
wi thin the impeller housing, producing a pumping action. On no
account should this pump be run dry. There should always be a spare
impeller and impeller cover gasket aboard.
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