Heat Exchanger; Replacing The Thermostat - Westerbeke BTG 8.5 Operator's Manual

COOLING SYSTEM
HEAT EXCHANGER
Cool raw water flows through the inner tubes of the heat
exchanger. As the engine coolant passes around these tubes
the heat of the internal engine is conducted to the raw water
which is then pumped into the exhaust system and discharged.
The engine coolant (now cooled) flows back though the
engine and the circuit repeats itself.
The engine coolant and raw water are independent of each
qther; this keeps the engine's water passages clean from the
harmful deposits found in raw water.
Heat Exchanger Service
After approximately 1000 hours of operation, remove, clean
and pressure test the engine's heat exchanger. (A local auto-
motive radiator shop should
be
able to clean and test the heat
exchanger).
NOTE:
Operating in silty and/or tropical waters may require
that a heat exchanger cleaning be peifonned more often then
every 1000 hours.
THERMOSTAT
A thermostat controls the coolant temperature as the coolant
continuously flows through the closed cooling circuit. When
the engine is first started the closed thermostat prevents
coolant from flowing (some coolant is by-passed around
the
thermostat to prevent the exhaust manifold from over-heat-
ing). As the engine warms up, the thermostat gradually opens.
The thermostat is accessible and can
be
checked, cleaned, or
replaced easily.
Carry
a spare thermostat and gasket.
Replacing the Thermostat
To avoid spilling coolant,
drain
the coolant down below the
manifold level
[REFER TO CHANGING COOLANTj.
Remove the cap screws and disassemble the thermostat
housing as -shown. When installing the new thermostat and
gasket, apply a thin coat of sealant on both sides of the
gasket before pressing it into
pi~.
Do not over-tighten the
cap screws. Replace the coolant in the manifold. Run the
engine and check for normal temperatures and that there are
no leaks at
the
thermostat housing.
THERMOSTAT
ASSEMBLY
COOLANT TEMPERATURE
ALARM SWITCH
14
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 onboard.
NOTE:
Electrolyiis
is
the result of each particular installf:ztion
and vessel location,
not
that of the engine.
HEAT EXCHANGER
D-RING
END GASKET
If the zinc anodes need replacement, hold the hex boss into
wj:rich the zinc anode is threaded with a wrench while
loosening the anode with another wrench. This prevents the
hex boss from possibly tearing off the exchanger shell. 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 l1eat
exchanger end gasket part number), 0-ring and cover, and
install a new zinc anode.
NOTE:
The
threads of the zinc anodes are pipe threads
and do
not require sealant Sealant should
not
be use4 as it
may
insulate
the
zinc from
the
metal of the heat exchanger
housing preventing electrolysis action on the zinc.
NEW
REPLACE CLEAN OFF
& REUSE
ZINC ANODES
,·