ENGINE
COOLING
CIRCUIT
THERMOSTAT
A thermostat, located near the manifold at the front
of
the
engine, controls the coolant temperature as it continuously
flows through the closed cooling circuit. When the engine is
first started the closed thermostat prevents coolant from
flow-
ing (some coolant is by-passed through a hole in the thermo-
stat to prevent the exhaust manifold from overheating). 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.
To
Replace
the
Thermostat
THERMOSTAT
ASSEMBLY
(M-358
SHOWN)
Remove the two cap screws and disassemble as illustrated.
When assembling the new thermostat and gasket put a thin
coat
of
sealant on both sides
of
the gasket before pressing in
place. Run the engine and check for normal temperatures and
that there are no leaks at the thermostat housing.
Heat
Exchanger
The heat exchanger is a copper tube which encloses a num-
ber
of
small copper tubes. Raw water is pumped through the
small copper tubes and the freshwater coolant from the
engine is circulated around the copper tubes. The raw water
removes heat from the freshwater coolant.
To
keep the heat
exchanger operating efficiently, it should be removed from
the engine every
1000 hours to be thoroughly cleaned and
pressure tested.
HEAT
EXCHANGER
ZINC
ANODE
Zinc
Anode
REPLACE
CLEAN
&
REUSE
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. The area in the exchanger where the anode
is located should periodically
be
cleaned
of
anode debris.
RAW
WATER
INTAKE
STRAINER
NOTE:
Always install
the
strainer at or below
the
waterline
so
the
strainer will always
be
self-priming.
A clean raw water intake strainer is a vital component
of
the
engine's cooling system. Include a visual inspection
of
this
strainer when making your periodic engine check.
The water
in the glass should be clear.
Perform the following maintenance after every I 00 hours
of
operation:
1.
Close the raw water seacock.
2.
Remove and clean the strainer filter.
3. Clean the glass.
4. Replace the sealing washer
if
necessary.
5. Reassemble and install the strainer.
6.
Open the seacock.
7. Run the engine and check for leaks.
NOTE:
Also follow
the
above
procedure after having
run
hard
aground.
If
the engine temperature gauge ever shows a higher than nor-
mal reading, the cause may be that silt, leaves or grass may
have been caught up in the strainer, slowing the flow
of
raw
water through the cooling system
SEACOCK
'sEALING
··WASHER
4
.,Unlvarsal
RAW
WATER
INTAKE
STRAINER.
'.
[TYPICAL].
MARINE POWER
16
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