Installation manual
COOLING
SYSTEM
RAW
WATER
PUMP(#42026)
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 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. The neoprene impeller
has a limited lifetime and must be inspected regularly.
NOTE:
Should a failure occur with the
pump~
internal parts
(seals
and
bearings), it may be more cost effective to purchase
a new pump
and
rebuild the original pump as a spare.
Inspecting/Changing
the
Raw
Water
Pump
Impeller
Close the raw water intake valve. Remove the pump cover
and, with the proper size impeller tool, carefully pry the
impeller out
of
the pump (the impeller can be pried out using
a pair
of
screwdrivers
if
an impeller puller is unavailable. Take
care not to tear the impeller). Install the new impeller and
0-ring. Move the blades to conform to the curved cam plate
and push the impeller into the pumps housing. When
assembling, apply a thin coating
of
lubricant to the impeller
and gasket.
Open
the
raw
water
intake
valve.
Run the engine and check for leaks around the pump. Also
check for water discharge at the stem tube. Absence
of
water
flow indicates the pump has not primed itself properly.
NOTE:
Never allow the pump to run
dry.
Even a short period
of
dry running may destroy the impeller.
INSPECT
THE
0-RING
AND
IMPELLER.
REPLACE
IF
THEY
SHOW
SIGNS
OF
WEAR.
THE
PIN
FITS
INTO
THE------
IMPELLER
SLOT
IN
THE
SHAFT.
~
ยท
LIGHTLY
GREASE
THE
PUMP
CHAMBER,
0-RING,
AND
IMPELLER
WITH
GLYCERIN.
A
CAUTION:
If
any
of
the
blades
have
broken
off
the
impeller,
they
must
be
located
to
prevent
blockage
in
the
cooling
circuit.
They
often
can
be
found
in
the
heat
exchanger
RAW
WATER
INTAKE
STRAINER
NOTE:
Always install the strainer at
or
below the waterline so
the strainer will always be self-priming.
A clean raw water intake strainer is a vital component
of
the
engine's cooling system. Include a visual inspection
of
this
strainer when making your periodic engine check. The water
in the glass should be clear.
Perform the following maintenance after every
100
hours
of
operation:
1.
Close
the
raw
water
seacock.
2.
Remove and clean the strainer filter.
3. Clean the glass.
4. Replace the sealing washer
if
necessary.
5. Reassemble and install the strainer.
6.
Open
the
seacock.
7. Run the engine and check for leaks.
NOTE:
Also follow the above procedure after having run hard
aground.
If
the engine temperature gauge ever shows a higher than
normal reading, the cause may
be
that silt, leaves or grass
may have been caught up in the strainer, slowing the flow
of
raw water through the cooling system.
TYPICAL
RAW
WATER
INTAKE
STRAINER
(Owner
Installed)
DRAINING
THE
RAW
WATER
COOLING
SYSTEM
When freezing temperatures are expected, the cooling system
can be drained by loosening the raw water pump's cover
plate screws. This should allow the water to drain out
of
the
pump and also drain back to the strainer.
Open the raw water petcock/plug on the heat exchanger to
allow the raw water to drain.
Engines & Generators
17