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COOLING SYSTEM
DESCRIPTION
Westerbeke marine diesel engines are designed and equipped
for fresh water cooling. Heat produced in the engine by com-
bustion and friction is transferred to fresh water coolant
which circulates throughout the engine. This circulating fresh
water coolant cools the engine block, its internal moving
parts, and the engine oil. The coolant is, in tum, cooled by•
raw water, and the raw water carries the transferred heat over-
board through the exhaust system. The fresh water coolant
and raw water circuits are independent of each other. Using
only fresh water coolant within the engine allows the cooling
water passages to stay clean and free from harmful deposits.
Coolant Pump
The fresh water coolant is pumped through the engine by a
circulating pump. The coolant passes through the thermostat
into the manifold, to the heat exchanger where it is cooled,
and returned to the engine block via the suction side of the
circulating pump.
Raw Water Pump
The raw water flow is created by a positive displacement
impeller pump. This pump draws water directly from the
raw water source (ocean, lake, or river) through a hose to the
water strainer. The raw water passes from the strainer
through the raw water pump to the heat exchanger, then to the
transmission oil cooler (propulsion engines only). The raw
water is then discharged into the water-injected exhaust el-
bow, mixing with and cooling the exhaust gasses. This mix-
ture of exhaust gas and raw water is discharged overboard by
the engine's exhaust gas discharge pressure.
TO TRANSMISSION
Oil COOLER (PROPULSION
ENGINES ONLY)
The raw water pump is a self-priming, rotary pump with a
non-ferrous housing and a neoprene impeller. The impeller
has flexible vanes which wipe against a curved cam plate
within the impeller housing, producing the pumping action.
This pump must not be run dry as water acts as a lubricant
for the impeller.
Heat Exchanger
The engine heat is transferred externally from the fresh water
coolant to the raw water in the heat exchanger. The raw
water flows through tubes in the heat exchanger while the
fresh water coolant flows around the tubes. The engine heat
is conducted from the fresh water coolant through the tube
walls to the raw water.
Thermostat
A thermostat, located near the manifold at the front of the
engine, controls the coolant temperature as the coolant contin-
uously flows through the closed cooling circuit. When the
engine is first started, the closed thermostat prevents coolant
from flowing (some coolant is by-passed through a hole in
the thermostat to prevent the exhaust manifold from over-
heating).As the engine warms up, the thermostat gradually
opens.
When the engine is started cold, external coolant flow is pre-
vented by the closed thermostat (although some coolant flow
is bypassed around the thermostat to prevent the exhaust
manifold from overheating). As the engine warms up, the
thermostat gradually opens, allowing the engine's coolant to
flow unrestricted to the external portion of the cooling system.
COOLANT
TEMPERATURE
SWITCH
0:
TO WATER HEATER
BOTIOMINLET
COOLING SYSTEM
¢
COOLANT
•
RAWWATER
NOTE:
Anti-siphon
valve is not shown
. ' • ·.l
-"
~
-~
Engines
&
Generators
COOLANT ORAIN
located under
heat exchanger
near engine's
back plate
54
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