Automatic Bilge Pumps -
Wiring & Considerations for a Shallow Settee
INDEX - Pump,
Diode, Float Switch,
Manual Switch, Wire
Gauge, Harness Install, Power, Backup Power,
WIRING a BILGE PUMP - The primary
job of a small electric bilge pump is to remove nuisance water or light flooding. It is not an emergency pump designed to
empty a half submerged hull. Few
SJ23s have enough power to operate an emergency pump but any
pump can buy you
extra time to don a life jacket, find the leak and hopefully keep the
boat afloat till you get to shallow water. Beach it if you have to! The following points have
criteria to protect you and your boat from a catastrophe.
- FAIL SAFE POWER - Panache's 3 pumps are
connected to an alarmed circuit breaker (Tech Tip E02,
Bkr 15) wired directly to
battery buss BB2.
Wired as such, each bilge pump
can operate automatically by it's float switch or manually by the
toggle switches, all with the main power switch off.
NEVER connect a switch in this circuit that
can shut the power off, unless the switch is alarmed to indicate it is
- PUMP & CONNECTOR - Each bilge pump
is connected to its wire harness through a
sealed connector that can be handled with wet hands. The
pins are greased to protect against corrosion. All pumps are
installed, using the same style connector and wiring so they can be
interchanged for redundancy,
removed for service
or dried for winter storage.
- To this end each settee
pump, float switch and relay combination is installed on an base aluminum plate
and is treated as a "unit". Each unit is protected
by a SS fence from the gear stored under the
Tech Tip C12
for this criteria.
A centrifugal style pump can move water faster than a
A centrifugal pump MUST be primed otherwise it can't
move water. An immersed pump is automatically primed.
- A centrifugal pump MUST be capable of large volume pumping with
of head. This one exceeds 10'.
- A check valve in the discharge hose can prevent water from draining
back into the bilge after the pump is shut off. But it can also prevent
the pump from self priming. Confirm functionality prior to
fabricating your system.
A electric centrifugal pump can move more water with the correct polarity applied than the opposite polarity. Verify your connection.
- PROTECTION DIODE - An electric bilge pump is an inductive load that will send a
large voltage pulse back into the wiring harness when it's shut off.
For that reason each pump requires a diode across its leads to short circuit
the pulse, thereby protecting
sensitive electronic devices (LEDs) connected to the wiring harness. You may never experience
this problem if the cabin lights are switched off when the pump shuts down
but one day you will wonder what the ____ happened to the lights? See Tech Tip E11.
- I installed this diode electrically next to
each pump on a Jones terminal strip
as it is the most effective place. Don't install the diode
buried somewhere in the wiring harness as you will
forget where it is.
SETTEE FLOAT SWITCHES - For the shallow settee bilges I
repurposed an external float switch that operates in
only 1/2" deep water. The failure of the reed relay contacts in a float switch is
due to contact arcing caused by surge
current when a bilge pump (DC motor) starts. But if
the reed relay of the float switch operates a sealed automotive relay
which in turn operates the bilge pump, there is no arcing on the float
switch contacts due to the
low coil current (~80MA). The automotive relay contacts are designed to handle high current and
can easily control a bilge pump. Problem solved with no standby
power drain, hence the relay circuit below that works for Panache's settee
This configuration should last a million cycles. See Tech Tip E02 for
pin assignment on Term Strip #1.
NOTE - Don't operate the
reed relay with only
micro-amps of current as it will eventually go intermittent. It should be in the
milliamp range to keep the contacts clean.
Possible Trouble - Float switch failure may also be due to a hull pounding
hard on waves damaging the delicate reed relay as it bounces in a dry
bilge. Each bounce will cycle the pump power, pitting the contacts. While this problem is
more prevalent on a power boat skipping across the waves than on a
sailboat sliding over the waves, you should be mindful of this.
It could be an issue in the shallow settee "bilge" of an SJ23.
Stilling Well - Consider installing the float switch in a "stilling well" to dampen
the surface so it measures water depth more accurately minimizing
start/stop cycles due to water sloshing. Water in a "stilling
almost like installing an electronic start delay timer of ~5 sec (prevent false starts)
and a drop out delay timer of ~15 sec (to empty the bilge and drain
hose). This timer might be useful on its own merit. With either of these you'll find the pump cycles less which
is a more satisfactory long lasting operation.
COCKPIT FLOAT SWITCH - Each bilge pump should be
wired to operate automatically through a float switch
with a manual override switch just in case the float switch doesn't
work. Most mechanical float switches start a pump when the water
is about 2" deep and stops when it is 3/4" deep. The way I see
it, this style float switch provides automatic pumping for lots of
water in the bilge and the manual switch can pump the remainder of the
water. Console yourself
with the fact that the bilge is basically empty and the boat can
easily handle this bit of nuisance water. This is the
simplest configuration and works well for the SJ23 port cockpit locker. The float switch
in the drawing below is internal to the cockpit pump so the wiring harness is connected directly to those
wires. See Tech Tip E02 for
pin assignment on Term Strip #1.
MANUAL OVERRIDE SWITCHES - A manual override switch
can be used to remove nuisance water below what a float switch can
detect or to bypass a failed float switch to
empty a bilge
RIGHT NOW! Install the
toggle switch in a
logical dry place above high water and label it. If the switch is
the open, protect it
with guards against accidental operation!
- The 3 manual switches on Panache are
installed on the breaker
back panel where
they are convenient to use and dry to prevent corrosion.
See Tech Tip E02.
Pin assignment is on Term Strip #1.
WIRE GAUGE - Use at least #12 stranded wire
(tinned if you like) so the pump receives the highest possible
voltage. All splices are crimped, soldered, sealed and connector
pins are greased to prevent corrosion.
- I tested Panache's
new settee pumps (1.5 A) with 20' of #12 wiring and it moved a gallon of water
in the same time as when connected via the thin manufacturer leads.
With that I fabricated a longer wire harness for each
pump (cockpit pump shown), added a connector at the pump end, then labelled
and tested each to confirm they operate prior to
WIRE HARNESS INSTALL -
"This explanation gets kind of convoluted but
bear with me". Where a wire harness goes through
a bulkhead the wood core was sealed with epoxy, a thru hull fitted to provide chafe protect and sealed with butyl rubber to
stop water flow. Butyl is used in case a fitting has to be
- The wire harness
for the cockpit locker goes up from the pump to the top of the
locker through a bulkhead hole into the cabin. The thinner upper
portion of the bulkhead is solid 1/8" fibreglass.
- The wire harness for
the port settee pump goes aft in a wood
cable tray mounted inside the top of the settee.
The tray lines up with a hole drilled through the bulkhead
into the cockpit locker. Once inside the locker
the harness goes up to the top of the locker (with the cockpit pump
harness), then both go back through the
bulkhead into the cabin.
NOTE - The thicker bottom half of the bulkhead at the front of the
consists of 1/4" plywood covered with fibreglass. A hole is
drilled to accept a vinyl cable guide for chafe
protection. The exposed wood
in the cable hole is sealed with epoxy to protect the wood.
- From there both harnesses go under the companionway across to the starboard side
behind the breaker panel.
- The wire harness for the starboard settee
goes aft from the pump in a wood cable tray at the top,
then up to the starboard gunwale to end behind the breaker panel.
- All 3 harnesses go forward, through a hole I drilled in the 3" wide bulkhead, to
end behind the breaker panel for electrical connection.
Always install cable from the load to the power source
where the last connection is to be made. Leave some slack at
both ends for servicing. Make resistance measurements to confirm
all is OK then switch the power on to do an operational test. Now
that a pump is at the bottom I'll have to drain this bone dry for winter.
- DISCHARGE HOSE - For clarity the discharge tube is not shown on
the settee pump below. This tube goes up from the pump to a
wood cable tray at the top of the settee, aft through a bulkhead (sealed
fitting), then up to the top of the cockpit where it drains into the
foot well. From there it flows through the cockpit drains back into the drink.
BACKUP POWER - A boat connected to shore power
can usually draw
more power than it can use. Unfortunately dock power has a notorious way of
being switched or tripped off when you need it most.
Then there is the inevitable curse of forgetting to plug the boat
in before you leave! For this reason,
should also have a solar panel to charge the battery. Given a short run time of the pump and sufficient sun, the
solar panel should be able to maintain pump operation. Hopefully
for you to plug the leak.
- OPERATIONAL TEST - It's wise to operate the each pump manually every now and then to verify
operation. The advantage of a mechanical float sensor versus a
solid state sensor is that you can lift the automatic float switch with your finger and the pump
should run. But mechanical is not perfect either!
Operate the manual override switch and the pump should run. I know
many sailors who test their pump each time they leave their
boat. On the other hand, there are lots who don't! Go
A centrifugal pump can be run dry for a few seconds without
damaging the motor. At right is my prototype settee bilge pump that has run for 2 seasons without failure. The flow rate is more than adequate for the tiny amount of water that settles in the settee.
- While a numerical counter for pump operation cycles is useful to understand the extent of a problem, I don't plan to install
If you leave the bilge bone dry, it should still be bone dry when you
return. Think this logic through! Just say'n.
- PARTS (or equivalent)
- Submersible Bilge Pump;
CK-181DC, rated at 200 GPH, 1/37 HP, 12V, carbon brush motor, polypropylene impeller.
Tested to empty a 23L bucket in 1 min. & measured head of 10'.
3-way flat trailer connector, (water proof if greased).
Water level sensor, 400MM, N.O. contacts.
Bosch Automotive Relay, (water proof).
- Jones Terminal Strip;
- Insulated terminal fittings. (crimped, soldered & greased).
- 3/8" & 3/4" vinyl tubing.
- Two 1/2" hose thru-hull fittings,
- One 3/4" hose thru-hull fitting,
- All the consumable parts I grabbed from my stash.
- 4" wide SS fence to protect pump from items stored in settee.