ENGINE
COOLING
CIRCUIT
THERMOSTAT
A thermostat, located ncar 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.
THERMOSTAT
.
_._._._
..
_
..
GASKET
~I
THERMOSTAT~
i
THERMOSTAT
HOUSING
To
Replace
the
Thermostat
SEAL
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.
14
RAW
WATER
COOLING
CIRCUIT
The
raw water flow
is
created
by
a positive displacement
impeller pump. This
pump
draws water directly from the
ocean, lake,
or river from a through-hull opening through a
hose to the water strainer.
The
raw water passes from the
strainer through the
pump
to a heat exchanger (through the
heat exchanger tubes) where
it
cools the engine's circulating
fresh water coolant. The raw water
is
then discharged into the
water injected exhaust elbow, mixing with, and cooling the
exhaust gasses. This mixture
of
exhaust gas and
raw
water
is
driven through the stern tuhe and overboard.
Raw
Water
Pump
TIle
raw water pump
is
a self-priming, rotary pump with a
non-ferrous housing and a neoprene impeller. The impeller
has flexible vanes which wipe against a curved cam plate
within the impeller housing, producing the pumping action.
On
no account should this
pump
be run dry
as
water acts as a
lubricam for the impeller. There should always
be
a spare
impeller and impeller cover gasket aboard (an impeller kit).
Raw
water pump impeller failures occur when lubricant (raw
water)
is
not present during engine operation. Such failures
are not warrantable, and operators are cautioned
to
make sure
raw water flow
is
present at start-up.
RAW
WATER
PUMP
WEAR
PLATE
HOUSING
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