Cooling System - Westerbeke BTD 8.0 KW 60Hz 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
engine. 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 automotive 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
engine. 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 external portion of the cooling system.
a. Fresh Water Coolant (Antifreeze) Mixture.
It is recommended that a fres water and antifreeze mixture 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 feeling (see page 41 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 Witll 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.
In order to control the concentration of the mixture, mix the antifreeze and fresh water thoroughly before
adding it to the cooling system.
WESTERBEKE GENERATORS
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