Westerbeke BTDA 15.0 Operator's Manual & Installation Manual page 57

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 n. The hole is a bypass to prevent the exhaust manifold from overheating
during the engine's warm-up. Replacement thermostats
crumt
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 posnioned 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 ITseH 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.
If the zinc pencil needs replacement, hold
the hex boss into which the zinc pencil is
threaded with a wrench while loosening the
anode with another wrench. 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
NEW
RNOOE
REPLRCE
end cover. Replace the gasket (refer to your figure 5.25: Zinc Anode
engine model's heat exchanger end gasket
part number), cover, and install a new zinc pencil.
15.0KWBTDA
55
REPlACE
CLERN
DR
REPlACE
Westerbeke Generators