Table of Contents
Advertisement
COOLING SYSTEM
RAW WATER CODLING CIRCUIT
The raw water flow is created by a positive displacement
impeller pump. TIns pump draws water directly from the
ocean, lake, or river from a thru-hull opening through a hose
to the water strainer. The raw water passes from the strainer
through the pump to the 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-injecte4 exhaust elbow, mixing Witll, and cooling the
exhaust gasses. T1:rls nrlxture of exhaust gas and raw water is
driven thruugh the stem tube and overboard.
HEAT EXCHANGER
Cool raw water flows through the inuer 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 dis-
charged. The engine coolant (now cooled) flows back
through the engine and the circuit repeats itself.
NOTE:
Operating in silty arullor tropical waters may require
that a heat exchanger cleaning be peifol7ned more often then
every 1000 hours.
HEAT EXCHANGER
CLEAN OUT BOTH ENDS
ZINC ANODE.
DRAIN
~"1l'i~=::.--
'HAW
WATER DRAIN
-/"'''AN
OUT DEBRIS
CLEAN AND .
REUSE
A zinc anode, or pencil, is located in the raw water cooling
circuit witl:rln the heat exchanger. The pwpose 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 componeots 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.
NOTE:
ELectrolysis is the result of each pa/ticular instalLation
and vesseL Location; 1Wt thot of the engule.
NOTE:
The threads of the zinc atwdes,are pipe threads
WU}
do
not require sealant. Sealant should not be used as it may
insulate the zinc from the metal of tIle heatexc/wnger
1wusing preventing electrolysis action on the zinc.
RAW WATER PUMP
The raw water pump is a self-priming, rotary pump with a
non-ferrous housing and a Neoprene inlpeller_ The inlpeller
has fle«ible blades which wipe against a curved caro plate
within the inlpeller housing, producing the pumping action.
On
no acconn! should
this
pump be run dry_ There should
always be a spare inlpeller and inlpeller cover gasket aboard
(an inlpeller kit). Raw water pump inlpeller failures occur
wheo 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. The raw water pump should be inspected
periodically for broken or tom impeller blades. See
MAINTENANCE SCHEDULE.
.
NOTE:
Should a failure occur with the pumps internal parts
(seals ami bearings), it may be nwre cost efficient to
purchase a new pump alld rebuild the original pump as
a spare.
Changing the Raw Water Pump Impeller
Close fue raw water intake valve. Remove the pump cover
and, using an impelle, puller, screw drivers, or pliers,
carefully pry the inlpeller out of the pump. Install the new
inlpeller and gasket. Move fue blades to
COnfOffil
to the
curved carn plate and push the inlpeller into fue pumps hous-
ing. When assembling, apply a thin coating of lubricant to
the inlpeller
and
gasket. Opeo the raw water intake valve.
A
CAUTION:
If any
of
the vanes have broken off the
impeller, they must be found to prevent blockage in the
cooling circuit. They often can be found in the heat
exchanger.
INSPECTIDN: CHECK THE BASE OF
EACH BLADE BY BENDING VIGOROUSLY.
REPLACE THE IMPELLER
IF
THERE ARE
ANY CRACKS.
THE PIN FITS INTO THE
SLOT IN THE SHAFT.
LIGHTLY GREASE THE
PUMP CHAMBER, O-RING,
AND IMPELLER WITH
GLYCERIN.
INSPECT THE Q-RING
AND IMPELLER. REPLACE
IF THEY SHOW SIGNS
OF WEAR.
Engines
&
Generators
16
Advertisement
Table of Contents
Troubleshooting
