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
the fresh water which circulates throughout the en-
gine. This circulating fresh water cools the engine block and its internal moving parts. The heat is transferred
externally 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
fresh water is conducted through the tube walls
to
the sea water which is
pumped into the exhaust system and discharged overboard. In basic terms, 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 following paragraphs.
Fresh Water
Circuit
NOTE: Refer
to
paragraphs a and b
in
this section on 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, then
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 the exhaust manifold from overheating). As the engine warms
up, the thermostat
gradually opens, allowing the engine's fresh water coolant
to
flow unrestricted
to
the ex-
ternal portion
of
the cooling system.
a. Fresh Water
Coolant (Antifreeze) Mixture.
It is recommended that a freshwater and antifreeze mixture be used year-round. Water, when it freezes, ex-
pands sufficiently
to
split the heat exchanger and crack the engine block. A water/antifreeze mixture
of
proper concentration will prevent freezing (see page 26
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 antifreeze which is compatible with 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 inhibitors.
I n order
to
control the concentration
of
the mixture, mix the antifreeze and fresh water thoroughly before ad-
ding it
to
the cooling system.
25