first starts, it draws considerably more current than when
it’s running in what’s known as a steady state. This is
called “inrush” or “start-up load.” Bilge pumps experience
this, and it’s one of the reasons that the fuse or circuit
breaker value is specified as larger than the constant load
of the pump. If a smaller fuse were used that only took
into account the pump’s steady-state running load, it’s
likely that it would trip frequently at start up.
What happens, though, if the pump becomes jammed
or clogged with debris? Then, the pump is in a state of
suspended inrush or start up, and the current draw
remains high indefinitely. This is yet another reason that
wire should be sized conservatively; it should be fully
capable of supplying (because of its low resistance) full
locked-rotor current, which in turn will trip the breaker
or blow the fuse. If the wire is undersized, it’s unlikely
that enough amperage will reach the pump to cause the
fuse or breaker to trip. Instead, the pump might overheat
and catch fire in the event of a locked rotor. Pumps that
comply with current ABYC standards must include a
means by which power to the pump is shut off in the
event that they experience overheating, regardless of the
cause. Conversely, under normal conditions, in order to
meet the same ABYC guidelines, bilge pumps must be
capable of running continuously at their design voltage
for 24 hours.
OTHER ELECTRICAL CONCERNS
Further wiring considerations include connections,
terminations, wire routing, fuses, and circuit breakers.
As even the most inexperienced boat owner knows,
water (particularly sea water) and electricity do not mix
very well. Bilge pump installations are no exception to
this rule, and because of the important role they play in
the life of your boat, there’s virtually no margin for error.
Most submersible pumps are available with wire
leads that are long enough—usually about 6 feet—to
accommodate connections being made well above
maximum bilgewater levels. (Carefully check the specs
of a submersible pump regarding this option before
buying.) Ideally, connections should be made well
above bilgewater levels and should not have to rely on
waterproofing. A tinned copper terminal strip installed
4 or 5 feet above the bilge and then coated with
corrosion inhibitor means low-resistance connections
are secure yet accessible for inspection and testing.
If such an arrangement simply isn’t feasible, then
connections must be made as watertight as possible.
Regardless of location, conductors should be coated
with a conductant paste, such as Thomas & Betts Kopr-Shield, prior to installing crimp connectors. Connections
should be made using high quality resin-loaded heat-
Bilge Pumps, Part II
Debris is a bilge pump’s worst enemy. This strainer, installed
aboard a new vessel, has become impacted with “new-build
debris,” rendering the bilge pump it serves useless. The watch
phrase for pump-savvy cruisers is: keep your bilges clean and
free of all debris, no matter how small or seemingly insignificant.
shrink tubing, the kind that oozes sticky material when
heated. Be certain the resin completely encapsulates the
wiring as it exits the heat-shrink tubing ends. Secure
these connections as far above bilgewater as possible.
Remember: Water is the universal solvent. Given enough
time, it will leak through any “waterproof” seal.
Secure wiring leading from the pump in such a way
that it does not bridge any “air gaps”; that is, it should
not pass through open space between the pump and
a bulkhead or stringer. Instead, wiring should be
continuously supported and secured at least every 18
inches using wire ties or P-clips. If the wiring passes
over moving machinery, such as shafts or belts, use
metallic securing clips, rather than plastic clips.
Appropriately sourcing power for bilge pumps can
mean the difference between having a dry bilge and
finding your boat sunk at the bottom of its slip. My
preference is to supply bilge pumps with their power
