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A Few Tips for Easier Raw Water Pump Impeller Changing
by Tom Neale
This is a continuation of Tom's Tips from his section of
the www.boatus.com
web site. Go to his section there for many more tips on this
subject and others.
1. If you’re trying to squeeze the blades of a new impeller
to make it go inside the raw water pump, and you can’t
depress the blades sufficiently with your bare hands to get
it into the pump, try this trick. Get a good quality hose
clamp which doesn’t have perforations that can tear the
blades and which has rounded edges so as be less likely to
cut the blades. The clamp must be of sufficient diameter to
fit over the impeller. Put it around the impeller and begin
tightening down. You’ll have to find an area on the impeller
that’s close enough to the center of the impeller to
sufficiently depress the blades, yet sufficiently out from
the middle so that the impeller can be pushed into the pump
far enough to get onto the shaft. This may take some trial
and error. As you tighten down on the hose clamp, make sure
that the blades deflect in the right direction for the rotation.
Don’t over tighten and take care not to damage the blades.
The blades will still be extended enough so that you’ll
have to push and rotate, but it shouldn’t require quite
as much muscle. When the impeller is in deeply enough so that
it’s mated with the shaft, loosen the hose clamp with
a screw driver and slide it off the impeller. If you haven’t
gotten the impeller in far enough, it may pop back out of
the shaft. Hose clamps and other equipment can cut. Be careful.
2. Before you start your engine, you will, of course, have
opened the raw water through hull valve that you closed prior
to the job. If your engine or its pump is below the water
line (and there is no higher loop between the through hull
and the pump) let it sit a few minutes so that sea water will
find its way to the pump. This will help provide a well lubed
start up, thus lessening the chances of damage to the blades
from dry running.
3. Disable your engine from starting (as by unhooking the
battery) before you work on it.
Copyright 2005
Tom Neale
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