Raw Water Pump - Westerbeke 80N4 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 raw
water source (ocean, lake, or river) through a hose to the
water strainer. The raw water passes from the strainer
through the raw water pump to the heat exchanger (through
the heat exchanger tubes) where it cools the engine circulat-
ing fresh water coolant. The raw water is then discharged
into the water-injected exhaust elbow, mixing with and cool-
ing the exhaust gasses. This mixture of exhaust gas and raw
water is discharged overboard by the engine's exhaust gas
discharge pressure.
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 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
lubricant for the impeller. There should always be a spare
impeller and impeller cover gasket (an impeller kit) aboard.
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.
NOTE:
Should a failure occur with the pump's internal parts
(seals and bearings). it may be more cost efficient to pur-
chase a new pump and rebuild the original pump as a spare.
IMPELLER
INSPECTION: CHECK AT THE BASE OF
EACH BLAOE BY BENDING VIGOROUSLY.
REPLACE THE IMPELLER IF THERE
ARE ANY CRACKS.
WHEN INSTALLING: TAKE CARE TO ALIGN
THE IMPELLER KEYWAY WITH THE SHAFT
KEY. FOLD THE IMPELLER BLADES IN
EITHER DIRECTION (THEY WILL TURN IN
THE CORRECT POSITION WHEN THE
PUMP STARTS).
GREASE THE BLADES AND THE PUMP
CHAMBER WITH PETROLEUM JELLY
TO PROVIDE LUBRICATION FOR THE
FEW SECONDS THE PUMP HAS TO RUN DRY.
THE GREASE IMPROVES THE SEAL
OF THE BLADES AND MAKES INSTALLATION
EASIER.
THE O-RING GASKET
ONLY NEEDS TO BE .
REPLACED IF IT SHOWS ..
SIGNS OF WEAR.
Changing the Raw Water Pump Impeller
Close the raw water intake valve. Remove the pump cover
and, with the aid of an impeller puller, 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 pump's housing. When assem-
bling, apply a thin coating of lubricant to the impeller and
gasket.
Open the raw water intake valve.
To be certain the pump is operating properly, run the engine
and check the following:
o
Inspect the raw water pump for leaks.
o
After warm up, monitor the temperature gauge. It should
indicate a normal engine temperature.
o
Check aft. There should be a steady flow of water from
the stem tube.
A
CAUTION:
If any of the vanes have broken off the
impeller, they must be found to prevent blockage in the
cooling circuit. They onen can be found in the heat
exchanger.
Impeller Puller
WESTERBEKE recommends using an impeller puller to
remove the impeller, this will prevent damage to the blades
and to the edges of the pump housing.
WATER LEAKING HERE WOULD
INDICATE THE PUMP SEAL HAS
FAILED AND THE PUMP NEEDS
IMMEDIATE SERVICE.
~~~ft-*""---HOUSING
RAW WATER PUMP
Engines & Generators
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