Raw Water Cooling System; Heat Exchanger; Raw Water Pump - Westerbeke 5.5 EGCD Operator's Manual

COOLING SYSTEM
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 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-injected exhaust elbow, mixing with, and cooling the
exhaust gasses. This mixture of exhaust gas and raw water is
driven through the stem tube and overboard.
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 dis-
charged. The engine coolant (now cooled) flows back
through the engine and the circuit repeats itself.
NOTE: Operating
in
silty and/or tropical waters may require
that a heat exchanger cleaning be peifonned more often then
every 1000 hours.
HEAT EXCHANGER
CLEAN OUT BOTH ENDS
ZINC ANODE
NEW
. REPLACE . CLEAN AND .
. 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 on board.
NOTE:
Electrolysis is the result of each particular installation
and vessel location; not that of the engine.
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.
RAW WATER PUMP
The raw water pump is a self-priming, rotary pump with a
non-ferrous housing and a Neoprene impeller. The impeller
has flexible blades which wipe against a curved cam plate
within the impeller housing, producing the pumping action.
on
no
account
should
this
pump be run
dry.
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. 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 and bearings), it may be more cost efficient to
purchase a new pump and rebuild the original pump as
a spare.
Changing the Raw Water Pump Impeller
Close the raw water intake valve. Remove the pump cover
and, using an impeller pullef
1
screw drivers, or pliers,
carefully pry the impeller out of the pump. Install the new
impeller and gasket. Move the blades to conform to the
curved cam plate and push the impeller into the pumps hous-
ing. When assembling, apply a
thin
coatjng of lubricant to
the impeller and
gasket.·Q~n
the
raw
water intake valve.
·.··'
A
CAUTION:
"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.
INSPECTION: CHECK THE BASE OF
EACH BLADE BY BENDING VIGOROUSLY.
REPLACE THE IMPELLER IF THERE ARE
ANY CRACKS.
LIGHTLY GREASE THE
PUMP CHAMBER, 0-RING,
AND IMPELLER WITH
GLYCERIN.
INSPECT THE 0-RING
AND IMPELLER. REPLACE
IF THEY SHOW SIGNS
OF WEAR.
Engines
&
Generators
. 17