Westerbeke 7.6 KW BTD 60Hz Operator's Manual page 50

Thermostat
Generally, thermostats are of two types. One is simply a choking device which opens and closes as the
engine's temperature rises and falls. The second type has a bypass mechanism. Usually, this is a disc on
the bottom of the thermostat which moves downward to close off an internal bypass passage within the
head. Since 1980, each type of thermostat has a hole punched through it. The hole is a bypass to prevent
the exhaust manifold from overheating during the engine's warm-up. Replacement thermostats must
have this design characteristic.
Raw Water Circuit
The raw water flow is created by a gear-driven, positive displacement, neoprene impeller pump. The
pump draws raw water directly from the ocean through the sea cock and raw water strainer and passes the
water to the heat exchanger's raw water inlet. The raw water passes through the heat exchanger's tubes,
from which heat from the fresh water system that circulates around these tubes is absorbed, and then the
raw water is discharged from the cooling system overboard through the water-injected wet exhaust system.
Be sure to clean zinc debris from the area inside of the heat exchanger where the zinc anode is positioned
as this debris lays in front of these tube ends and blocks them.
Zinc Anode
A zinc anode, or pencil, is located in the raw water cooling circuit within the heat exchanger. The
purpose of the zinc anode is to sacrifice itself to electrolysis action taking place in the raw water cooling
circuit, thereby reducing the effects of electrolysis on other components of the system. The condition of
the zinc anode should be checked monthly and the anode cleaned or replaced as required. Spare anodes
should be carried on board.
NEIf
ANODE REPLACE REPLACE
CLEAN
DR
REPLACE
NOTE: Electrolysis action is the result of each particular installation and vessel location; not that
of the generator.
If the zinc pencil needs replacement, hold the hex boss into which the zinc pencil is threaded with a
wrencb while loosening the anode with another wrencb. This prevents the hex boss from possibly
tearing off the exchanger shell. After removing the zinc, note the condition of it. If the zinc is in poor
condition, there are probably a lot of zinc flakes within the exchanger. Remove the end of the heat
exchanger and clean the inside of all zinc debris. Always have a spare heat exchanger end gasket in
case the present one becomes damaged when removing the end cover. Replace the gasket (refer to
your engine model's heat exchanger end gasket part number), cover, and install a new zinc pencil.
WESTERBEKE GENERATORS
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