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Replacing Sea Water Pump Impeller
& Impeller
Troubleshooting Guide
The pump impeller is made of
neoprene rubber and this can be damaged in the case of water
deficiency if, for example, the sea-water intake has become
blocked.
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Marine Diesel Engine Maintenance Guide
The pump impeller is changed as
follows:
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Stop engine. Turn off sea
water inlet valve.
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Remove the cover from the
sea-water pump. Note that there is a risk of water
getting into the boat.
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With the help of two
screwdrivers pull the shaft with the pump impeller out
of the housing as far as necessary to reach the bolt
retaining the impeller. Place some kind of protection
under the screwdrivers in order not to damage the
impeller housing. Alternately, using channel-lock
pliers, slide jaws between blades of impeller, rotate
and withdraw.
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Pull the impeller off the
shaft. Clean the inside of the pump housing and fit the
new impeller. Always carry a spare impeller on board.
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Check that the pump coupling
is not damaged by trying to turn the pump impeller.
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Fit the cover with the
original gasket, which has the right thickness.
Impeller Troubleshooting Guide
This guide is designed to help
spot typical application problems that show up in flexible
impellers during normal use.
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Problem:
Pieces missing from blade tips, especially in
center of impeller. Edges look hollowed out or
eaten away. Pitting on end of impeller.
Cause:
Cavitation, i.e. too much vacuum at pump inlet,
fluid boils locally.
Remedies:
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Reduce pump speed.
- Increase
inlet pipe diameter.
- Reduce inlet
pipe length and restrictions.
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Problem: End
faces hard, polished, cracked, like carbon. Some
or all blades completely missing in severe
cases.
Cause: Dry running.
Remedies:
- Do not run
more than 30 seconds without liquid in pump.
- Stop pump as
soon as liquid is exhausted.
- Arrange pipe
work to trap liquid in pump on discharge
side; this prevents dry running for several
minutes.
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Problem:
Blades cracked about half way up their height.
Some pieces of blade missing.
Cause: Normal
end of useful life. Excessive outlet pressure
reduces impeller life. A crease on trailing side
of each blade can also indicate excessive
pressure.
Remedies:
- Reduce
pressure and/or pump speed.
- Increase
outlet pipe diameter.
- Reduce
outlet pipe length and restrictions.
- Can also be
due to dry running.
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Problem:
Blades permanently and excessively curved.
Cause: Long
term storage in pump. Normal end of useful life
(especially nitrile impellers used for bilge
pumping).
Remedies:
- Remove
impeller for long term storage.
- Refit
impeller to rotate in opposite direction.
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Problem: Worn
blade tips and faces. Worn impeller drive.
Cause:
Abrasive wear from pump or fluid. Worn impeller
drive can also be due to excessive pressure or
dry running.
Remedies:
- Pump should
continue to operate satisfactorily in worn
condition.
- Replace
severely worm pump parts.
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Troubleshooting guide
courtesy Jabsco
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When inspecting the impeller make sure the rubber has not
separated from brass bush.
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A temporary repair can be made with 5-minute epoxy.
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If impeller is missing blades -- where are they now? Check
down line, they are often stuck in outlet port of pump.
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Check for salt build-up at bends.
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Marine Diesel Engine Maintenance Guide
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