Installation 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
through
the
engine
and
the
circuit
repeats
itsel£
The
engine
coolant
and
raw
water
are
independent
of
each
other,
this
keeps
the
engine's
water
passages
clean
from
the
han11ful
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
111£lY
require
that a heat exchanger cleaning be
peifonned
more often than
every
1000 hours. ·
If the zinc anodes need replacement, hold the
hex
boss
into which 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 heat
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 used as it
may insulate the zinc from the metal
of
the heat exchanger
housing preventing electrolysis action on the zinc.
THERMOSTAT
A thermostat, located near the manifold at the front of the
engine, 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 through a
hole
in
the thermostat
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
spar·e
thennostat
and
gasket.
Replacing
the
Thermostat
To
avoid spilling coolant, drain the coolant
down
below the
manifold level
(REFER
TO
CHANGING COOLANT).
Remove the cap screws and disassemble the
the1mostat
housing
as
shown. When installing the new thermostat and
RAW
WATER
gasket, apply a thin coat of sealant on both sides of the
CLEAR
OUT
DRAIN
gasket before pressing it into place. Do not over-tighten the
ZINC
DEBRIS
cap screws. Replace the coolant in the manifold.
Run
the
ZINC
ANODE
engine and check for normal temperatures and that there are
A zinc anode, or
pencil,
is
located in the raw water cooling
~
leaks
at
the thermostat housing.
circuit within the heat exchanger. The purpose of having
zinc anodes
is
to
sacrifice them
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 canied on board.
NOTE:
Electrolysis action is the result
of
each pm1icular
installation
and
vessel location; not that
of
the engine.
CLEAN
&
REUSE
NEW
ZINC
ANODES
16
GASKET
APPLY
SEALANT
AT
ASSEMBLY
THERMOSTAT
ASSEMBLY