Boating

46 BOATINGMAG.COM APRIL 2016

 WHAT TO LOOK FOR

The Boat Doctor

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12"

Bilge-Pump Systems

ILLUSTRATIONS: TIM BARKER; PHOTO: JON WHITTLE

The ideal bilge-pump system does not exist. Boats come in all sorts of sizes and

are put to all sorts of uses in a variety of different environments. However, after

decades of boating I have developed a few prejudices, offered here as a sort of

buyer’s guide to bilge pumping. — Kevin Falvey

[ 1 ]TWO-PUMP MINIMUM

Redundancy is tough to beat where

safety is concerned. I like pumps

arranged one higher than the

other, the high one never seeing

service — and so not wearing out —

unless things get really bad.

[ 2 ] PUMPS GALORE Bilge

pumps should be installed in all

compartments that can hold water.

Often there will be space between

bulkheads beneath the cabin sole,

for instance, or beneath the sole of

a center-console head. Check it out.

SMOOTHBORE HOSE Forget the

cheap corrugated stuff sold as

“bilge hose.” The ridges decrease

our pumps’ capacity by 20 percent.

Smoothbore hose, which is either

reinforced vinyl [ 3 ] or sanitation

hose [ 4 ], is more durable and

doesn’t impede fl ow.

[ 5 ]HOT WIRED Bilge pumps are

the only circuit that should be wired

directly to your batteries, according

to the American Boat and Yacht

Council (ABYC). Take power from

the back of your selector switch

in order to tap more than just

one battery.

[ 6 ]NO CHECK VALVES This is

also an ABYC requirement. If the

amount of water remaining in

the discharge hose fl ows back and

sets off your fl oat switch, raise the

switch a little higher to avoid pump

cycling. Use the manual switch to

remove more water.

[ 7 ]PREVENT SIPHONING

The discharge hose should be

run so that it comes up from the

pump higher than the level of

the discharge through-hull fi tting,

and then down to the fi tting. This

“riser loop” should be a minimum of

12 inches above the waterline.

[ 8 ]SWITCH ORIENTATION Float

switches should be installed fore

and aft, not across the beam, and

should have the hinge forward. This

prevents inadvertently energizing

the switch as the boat climbs on

plane or rocks in waves.

TOTAL CAPACITY I recommend

the following total-bilge-pump

capacities as rules of thumb. Boats

less than 20 feet: 1,000 gph; 20 to

25 feet: 2,500 gph; 25 to 32 feet:

4,000 gph; 32 to 36 feet: 6,000

gph; 37 to 45 feet: 8,500 gph.

PUMP RATINGS The number em-

bossed on the pump is optimistic.

There are formulas for calculating

actual gph versus rated gph based

on hose diameter, the height that

the water has to be lifted (the

“head”) and voltage. I simply count

on an actual capacity of 60 percent

the advertised rating.

[ 9 ]DON’T OVER FUSE If the

pump rotor locks up with debris,

the resistance will increase, but

amperage supplied will actually

drop (Ohm’s law). Of course, volt-

age is still supplied, and that is how

a pump can catch fi re without blow-

ing the fuse. Stick strictly to the

manufacturer’s recommendation

and use the lowest-rated fuse that

allows the pump to operate.

Electrical Connections for Bilge Pumps

Bilge pumps are pretty reliable. More often it’s the electrical

circuit providing them with power that fails, usually due to

corrosion. Use heat-shrink terminal connectors or coat the

connections with liquid vinyl, or both, when wiring bilge-pump

circuitry. — K.F.