Cooling System - Westerbeke BCG4.0KW Operator's Manual

COOLING 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 en-
gine. This circulating fresh water cools the engine block and tts 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 tt 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.
A freshwater and antifreeze mixture should be used year-round. Water, when
tt
freezes, expands sufficient-
ly to split the heat exchanger and crack the engine block. A water/antifreeze mixture of proper concentra-
tion will prevent freezing (see page 49 for an antifreeze/water mixture chart).
Use soft water with few impurtties, 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 which is made by a reli-
able 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.
In order to control the concentration of the mixture, mix the antifreeze and fresh waterthoroughly before ad-
ding it to the cooling system.
Westerbeke Generators 48