All those modern 'necessities' such as the
heads, engine cooling
intakes, stern glands etc, mean that many boats have more holes in
bottoms than a Dutch cheese.
Any of those through-hull
leak even if the seacocks are closed.
The essence of good seamanship is safety.
smallest open boat should have
some means of bailing.
A frightened boater can move a
lot of water with a
bucket, but only if he can get at it and is able to jettison it
A bilge pump is the answer for
any enclosed spaces which
are not easy to get that bucket into.
Even canoes can benefit from
having a small pump
How many pumps your boat
should have will depend on
Every hull is different
however, as a rough, starting
guide, a boat from 16ft to 26 ft / 5M to 8M in length should have at
pumps, 26 ft to 35 ft / 8M to 10M, at least three and anything above
should have at least four pumps.
It is worth remembering that
even on a small boat that one bilge pump is only adequate if it is
And the more bilge pumps you
have the more of your crew
will be able to help with the pumping.
By the same criteria, larger
boats should have at least
one more than the minimum if only as a back up.
Next thing to consider is
where the pumps are to be
A cabin cruiser, for instance
should have one which can
be operated from the cockpit and another from within the cabin and
referring to minimums.
Where the water accumulates is
another criteria to
Any sealed compartments which
don't drain to the
bilges should have their own dedicated pump.
Even if these compartments
won't hold much water it is
worth having a small pump to drain them if only to prevent water
The next problem is deciding what size or
pumping capacity your pumps should be.
The table I have drawn up below gives an indication of the capacities
should be aiming for however, there are several other factors to take
First do they all need to be the same size?
The bilge pump used for everyday needs, providing you don't have any
serious leaks won't require a large capacity.
And a smaller pump will require less energy to drive it whether its
energy or battery power.
Save your largest pump
On the subject of emergencies, which I sincerely hope none of us has to
with, a large capacity manual bilge pump could be operated by the
members of the crew while weaker members could help by pumping the
The next thing is how high the water has to be raised.
The height the water has
to be pumped vertically up
before it can discharge will reduce the amount the pump will be able to
This is something sail
boaters need to
consider, a pump which discharges on the
windward side will
have to lift the water higher than one emptying on the leeward but the
outlet could be underwater when the boat is well heeled.
The discharge rate will also be affected by the size of the piping,
smaller bore of pipe might reduce the flow-back but it will
the out flow.
When it comes to buying pumps I guess the best advice is to buy the
The efficiency and standard of the better know brands is exceptionally
unfortunately many manufactures complicate the process of choosing by
the capacities in different configurations.
A quotation in gallons or
litters per hour sounds
very impressive but how many of us could pump manually for an hour and
of our batteries would go flat in that time.
And the capacities quoted are rarely related to the height the water
has to be
When choosing, it is best to err on the safe side.
This table below is a very rough guide to the minimum pumping
should be aiming for.
When it comes to
choosing between electric, manual or engine driven bilge pumps I
believe it is
a good idea to hedge your bets
I would feel very vulnerable without at least one manually operated
I know that pumping is
work and few people can keep
it up for long but at least I don't have to worry about the electrics
Another advantage to the
modern diaphragm bilge pump is
that it is self priming.
And they can also be used
pump any stale air or more importantly gas out of the bilges, most have
few metal parts so the risk of causing a spark is
sure to choose one which
can be repaired and serviced
the other hand an electric pump with a float switch is perfect for
peace of mind when the boat is left unattended, providing the switch
the battery system up to running it for the necessary period of
For moving large amounts
water quickly and easily an
engine driven pump has got to be the best option but they are expensive
install and not a lot of use if you can't start the engine.
They also need to be mounted
at the front of the engine
which, for small boats is likely to be an issue due to lack of
Using the engine cooling
intake is not really an option
for small engines as the amount of water drawn by the impeller is not
And it is not worth the risk
of burning out the impeller
and wrecking the engine if it runs dry or it becomes blocked with
For small boats and canoes
there is nothing wrong with
the small plastic stirrup pumps.
However, few can be stripped
down easily so, keep that
bucket or cut down milk or oil carton handy as well.
I am perfectly aware that the majority of Wooden Boat aficionados are sensible folk. However, I need to point out that I am an amateur wooden boat enthusiast simply writing in order to try to help other amateur wooden boat enthusiasts. And while I take every care to ensure that the information in DIY Wood Boat.com is correct, anyone acting on the information on this website does so at their own risk.