Hello and welcome to Yachting Monthly's How To
series brought to you in association with GJW Direct
I'm Matthew Sheahan and over the course of 13 episodes
we're going to be dealing with some of the key issues when it comes to
maintenance and talking to some of the experts to get their tips.
One of the key checks once you've started your engine is to make sure that
your raw water cooling system is working properly
and we see that by water coming out of the side. Now on your yacht
this rubber hose will have gone through various
loops before it comes out the side of the hull.
So this is what you should be seeing coming out of the side of your boat
once you start your engine. You need to see a good flow of water.
If you don't see water coming out of your engine then you need to locate your
raw water pump. You can usually follow the ingress of
this straight from your sea strainer and they all look fairly similar.
Some of them are belt-driven such as this model. Some of them are gear
driven straight into the engine. The basic principle remains exactly the same.
You're going to have to take off your cover plate here
and check the state of the impeller
So as we take these off do be careful not to drop them in the bilge.
I would usually recommend in your boat putting a tea towel or similar below it
so that if you do inevitably drop one of these it's caught
in the tea towel rather than dropping down into a hole
you can no longer access
In here we can see the rubber impeller and what you'll be looking for are any
of these blades missing or damaged,
usually if the boat's been run dry or some debris has got into the system
you'll quite clearly see that some of these blades have been damaged.
This one actually looks good but we'll quickly show you how to pull it out
and and replace it with a new one. Now best practice is you use something
called an impeller puller which comes behind the impeller
and levers it out of the housing. It is quite easy to damage
the brass housing here and the rubber impeller itself.
The reality is it's quite unlikely you'll have one of these impeller pullers,
so we're going to use two pairs of pliers very gently
lever it out. It's not best practice but it's what most people are likely to
have to do.
All right so we're pulling it out here, being very careful
with the rubber fins and the housing it comes out nicely and we can now have
a really good inspection of it. This one looks in
really good condition - it's a new impeller
and we're very happy with that. Another problem you might face
is the wear plate inside this cam here is what forces
the blades to bend as it goes around producing the lift effect on the pump
and forcing the water through the system. So it is possible to get some damage or
some corrosion to the lift plate here and that is something you might also
need to replace, which is usually just held in place by a grub screw
from the other side of it. Have a good inspection of the housing.
Check there's no damage check the rubber o-ring around here
and once you replace it with a new impeller you should be pretty happy
that the system will start working again.
So if you're missing parts of your
impeller it is imperative before you run the engine again
that you find those missing parts. It's a simple matter of tracing
from your lift from your raw water pump take off the hose look for it in the
hose, find your way through to the heat
exchanger, open the ends of the heat exchanger
where you'll see copper tubing and find those bits of impeller.
If you do find that in the heat exchanger there's some very fragile
copper tubing in there so just be very careful with a piece of
electrical wire or similar to poke it through but make sure the
heat exchange is clear your hoses are clear and there's no
rubber left in the system. When you do come to
mount your new impeller it'll usually come with a little pack of grease
or lubricant. Just put that around the fins
and then you can put that into your raw water pump housing.
Make sure the impeller is facing the right way around - there is a front
and a back to the impeller and make sure that you bend the fins in
in the direction that the engine will turn when it goes back in.
Here's a little bit more, there you go, that's it that's it.
So there you can see the impeller's in and the fins are being bent
by the cam plate which produces the lift effect for the pump.
Put the face plate back on - you'll find there might either be a rubber o-ring
or there may be a paper gasket that sits between
the face plate and the body of the pump and you just need to make sure that's in
place and in good condition.
If the existing gasket is in good condition there should be no reason why
you can't reuse it if you don't have a spare one to put in
place. If you don't have the correct gasket
there are lots of marine sealants suitable to for
water for coolant that you could just rub around the
inside of the face plate there and that will certainly give you a good
seal until you can get home and and get the proper gasket in place.
Do just be careful as you tighten up the screws both when removing it and putting
it back on that you're using the right tool. It's
important not to round these these off.
Good practice however is that you replace your impeller
before it fails. For our skippers we don't really believe in having failed
impellers. If there's good checks to the raw water
supply before you fire it up, your sea-strainer is clean, there should be
no reason for your impeler to fail, so have a look on the packaging or the
manual. See what the service hours are for the impeller
and make sure you're changing it before it fails.
Well thanks for watching. I hope that was a help. Make sure that you like us,
make sure that you subscribe to us and stay in touch for the next episode