Cooung System - Westerbeke 7.0KW BCG-60HERTZ Operator's Manual

COOUNG SYSTEM
Description
Westerbeke marine gasoline 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 engine.
This circulating fresh water cools the engine block and its internal moving parts. The heat is transferred
extemallyfrom the fresh water to raw water by means of a heat exchanger, similar in function to an automotive
radiator. Raw 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 raw 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 raw water, and the raw water carries the transferred heat over the side through the
exhaust system. The fresh water and raw 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 used as the fresh water coolant, and for information on filling the fresh water system.
Fresh water is circulated through the engine by a belt-driven circulating pump, absorbing heat from the
engine. It 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 external portion of the cooling system.
A.
Fresh Water Coolant (Antifreeze) Mixture.
A freshwater and antifreeze mixture should be used year-round. Water, when
it
freezes, expands sufficiently
to split the heat exchanger and crack the engine block. A water/antifreeze mixture of proper concentration
will prevent freezing and promote better heat transfer (see next page 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
~rd
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. AJways
use antifreeze which is compatible with aluminum cooling system components and which is made by a
reliable manufacturer.
Never mix
different brands
of antifreeze.
Recommended antifreeze for year round
use is ZEREX or PRESTONE with rust inhibitors.
Make sure that the cooling system of the engine is well cleaned before adding antifreeze.
I n order to control the concentration of the mixture, mix the antifreeze and fresh water thoroughly before
adding it to the cooling system.
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