Operator`s manual
COOLING SYSTEM
Description
Westerbeke marine diesel engines are designed and equipped for fresh water cooling. Heat produced in
the engine by combustion and friction is transferred
to
fresh water which circulates throughout the engine.
This circulating fresh water cools the engine
block and its internal moving parts. The heat is transferred ex-
ternally from the fresh water
to
sea water
by
means
of
a heat exchanger, similar
in
function
to
an automo-
tive radiator.
Sea water flows through the tubes of the heat exchanger while fresh water flows around the
tubes; engine heat transferred
to
the fresh water is conducted through the tube walls
to
the sea water which
is then pumped into the exhaust system where
finally it is discharged overboard. In other words, the engine
is cooled
by
fresh water, the fresh water is cooled
by
sea water, and the sea water carries the transferred
heat over the side through the exhaust system. The fresh water and sea water circuits are independent of
each other. Using
only fresh water within the engine allows the cooling water passages
to
stay clean and
free from harmful deposits. The two independent circuits and their components are discussed in the
follow-
ing paragraphs.
Fresh
Water
Circuit
NOTE: Refer
to
paragraphs A and B
in
this section for the recommended antifreeze and water
mixture
to
be used as the fresh water coolant, and for information on filling the fresh water
system.
Fresh water is pumped through the engine
by
a belt-driven circulating pump, absorbing heat from the en-
gine. The fresh water coolant circulates through the engine's block absorbing heat, then passes through
the thermostat into the exhaust manifold,
to
the heat exchanger where it is cooled, and then is returned
to
the engine block through the suction side of the fresh water circulating pump. When the engine is started
cold, external fresh water flow is prevented
by
the closed thermostat (although some fresh water flow is
bypassed around the thermostat
to
prevent exhaust manifold from overheating). As the engine warms up,
the thermostat gradually opens,
allowing full flow of the engine's fresh water coolant
to
flow unrestricted
to
the external portion of the cooling system.
A.
Fresh Water Coolant (Antifreeze) Mixture.
A freshwater and antifreeze mixture
should be used year-round in the cooling system. Water, when
it
freezes,
expands sufficiently
to
split the heat exchanger and crack the engine block. A water/antWreeze mixture
of
proper concentration will prevent freezing (see page
53
for an antifreeze/water mixture chart).
Use soft water with few impurities, such as tap water (potable water)
or
rainwater. Never use hard
or
foul
water. Use
of
hard water
or
water containing impurities will lead
to
the collection of scale in the engine and
heat exchanger which
will reduce the cooling system's efficiency.
Antifreeze of
poor
quality
or
without rust inhibitors will cause corrosion within the cooling system. Always
use antrrreeze which is compatible wah aluminum cooling system components and is made by a reliable
manufacturer. Never mix different brands
of
antifreeze.
Make sure that the
cooling system
of
the engine is well cleaned before adding antifreeze. Recommended
antifreeze for year round use is
ZEREX
or
PRESTONE with rust inhiMors.
In
order
to
control the concentration of the mixture, mix the antifreeze and freshwater thoroughly before ad-
ding it
to
the cooling system.
Westerbeke Diesel Engines 52