Maintenance: Cooling System; Figure 17: Coolant System - Westerbeke 9.5 MCGA 60 Hz Operator's Manual

Operator Manual for Gasoline Generators
5.3

Maintenance: Cooling System

CAUTION: Proper cooling system maintenance is critical. Many premature engine failures can be traced back to cooling
system corrosion.
5.3.1 Fresh Water Cooling Circuit
Westerbeke marine 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 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 the fresh water is conducted through the tube walls to the sea water which is then pumped
into the exhaust system where finally it 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.
5.3.2 How to Drain and Refill the Coolant
Over time, without proper maintenance, the coolant can become contaminated. This condition can lead to
overheating problems. Follow these steps to change (drain and refill) the coolant.
1. The engine coolant must be changed as directed in 5.1 Maintenance Schedule.
2. If maintenance is due, allow the engine to cool before continuing. For initial fill, skip to step 5.
CAUTION: The engine must be allowed to cool down before attempting these procedures. Not only is the surface of the
engine hot, but coolant temperatures can exceed 190° F (87° C).
3. Drain the engine coolant.
a. Drain the engine block.
Remove the in-board drain plug on the heat exchanger.
b.
Remove the pressure cap from the water jacketed exhaust manifold.
c.
4. Re-install the coolant drain plugs.

Figure 17: Coolant System

5 Maintenance
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