SJ23 Tech Tip E16, (Updated 2023-08-10) Bob Schimmel


Automatic Bilge Pumps - Wiring & Considerations for a Shallow Settee Bilge Pump.
INDEX - Pump, Protection Diode, Settee Float Switch, Stilling Well, Manual Switch, Wire Gauge, Harness Install, Power, Backup Power, Test, Parts.

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 electrical 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! 

A SJ23 does not have a central bilge where all water can be conveniently pumped out of.  Instead it has 2 settees and a cockpit locker where water collects.  The water under the forward berth flows into one of the settees.  For this reason 3 pumps are required; one in each settee and another in the port cockpit locker.  Panache's portable deck wash pump could be considered as the fourth pump for the cabin.  The following points have important overlapping criteria to protect you and your SJ23 from a catastrophe. 

  1. FAIL SAFE POWER - Panache's 3 pumps are connected to an alarmed circuit breaker (Tech Tip E02, Bkr 15) wired directly to the constant battery buss BB2.  Wired as such, each bilge pump can operate automatically by it's float switch or manually by a toggle switch, all with the main power switch off.
    CAUTION - NEVER connect a switch in this circuit, unless it is alarmed to indicate power is off. 
  2. PUMP & CONNECTOR - Each bilge pump is connected to the boat wire harness through a robust sealed connector with greased pins to protect against corrosion while immersed.  The connectors can be handled safely with wet hands.  All pumps are installed, using the same type of connector and pin out 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 aluminum base plate and is treated as a "unit".  Each unit has a SS fence to protect it from gear stored under the settee.  See Tech Tip C12 for this criteria. 
    A centrifugal style pump can move water faster than a displacement pump.
    - An immersed pump is automatically primed which is when it can move water.
    - A centrifugal pump MUST be capable of pumping a large volume with a minimum 4' of head.  This one exceeds 10'.
    - An electric centrifugal pump can move more water with the correct polarity applied than the opposite polarity.  Perform this test prior to electrical connection.  One of Panache's pumps was backward from the manufacturer.
    - 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, restrict water flow or freeze during winter.  This is why they are NOT installed on Panache.
  3. PROTECTION DIODE - An electric bilge pump is an inductive load that can send a large voltage pulse back into the boat wiring harness when it shuts 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 hell 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.
  4. 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 pumps.  This configuration should last a million cycles.  See Tech Tip E02 for pin assignment on Term Strip #1.
    NOTE - Don't operate a reed relay with only micro-amps of current as it will eventually go intermittent.  The current 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 well" is almost like installing an electronic timer (start delay of ~5 sec and a drop out delay of ~15 sec) to prevent false starts.  This timer might be useful on its own merit though.  With either or both of these timers the pump will cycle less, which is a more satisfactory long lasting operation. 
    - An alternative to using a timer is to us a dry bilge pump.  Do a search for 'dry bilge systems" reveals a useful bilge pump that can suck all the water from a shallow bilge: Seaflo with a YouTube video.

    COCKPIT BILGE PUMP - 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 the remaining 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 the power distribution.  See Tech Tip E02 for pin assignment on Term Strip #1. 


  5. 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 installed in 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.
  6. 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 installation. 
  7. 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 is fitted to provide chafe protection and is sealed with butyl rubber to stop water flow.  Butyl is used in case a fitting has to be opened later. 
    - 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 cockpit locker 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.
  8. 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.
  9. 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, your boat 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 long enough for you to plug the leak.
  10. 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 figure. 
    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 one.  If you leave the bilge bone dry, it should still be bone dry when you return.  Think this logic through!  Just say'n.
  11. 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'. 
    - Connector; 3-way flat trailer connector, (water proof if greased).
    - Diode; 1N4007.
    - Float Switch; Water level sensor, 400MM, N.O. contacts.
    - Relay; Bosch Automotive Relay, (water proof).
    - Jones Terminal Strip; Ebay.
    - Insulated terminal fittings. (crimped, soldered & greased).
    - 3/8" & 3/4" vinyl tubing.
    - Two 1/2" hose thru-hull fittings, 24067
    - One 3/4" hose thru-hull fitting, 24069
    - All the consumable parts I grabbed from my stash.
    - 4" wide SS fence to protect pump from items stored in settee.




Fig 1 - Here I slid the false floor aft ~6" to reveal the blue bilge pump on the bottom of the cockpit locker.  While it isn't secured to the floor, the stiff discharge hose and being wedged by the false floor support it upright to prevent the float switch from false operation. Fig 2 - I temporarily removed the Tiller Pilot storage tube to install the transom thru-hull.  The vinyl drain hose is fully supported in the wood tray on the left.


Fig 3 - This stream of water is leaving the cockpit locker almost at full flow.  The flow starts slower than this but soon becomes a full stream as shown.  I purposely placed the thru hull fitting where the stream would flow between 2 rungs of the boarding ladder. 
Hmmm, this could be interesting for a person climbing up the ladder.  Stop that!



Fig 1 - The SS fence below is temporary to determine suitable protection.  The pump assembly is bolted to the settee wall so it can't tip over to prevent the float switch from activating the pump.  The wire and hose above are supported in a wood cable tray at the top of the settee.


Fig 2 - Drilling through a water tight compartment is always a nervous time.  Fortunately I could see and touch both sides so alignment was not a problem.  The skin on the port side of the cockpit foot well is single skin 1/8" fibreglass and dual skin 1/8" fibreglass on the starboard side.  A hole saw makes a very clean cut.


Fig 4 - Pumping from the starboard settee into cockpit.


Fig 3 - Completed thru hull fitting installation on starboard side of the cockpit. 
- The inside of the barbed end was bevelled to reduce debris obstruction and maximize flow. 
- The hose clamp will be replaced with a spring style so it stays snug all the time.  This screw style has a nasty habit of loosening with time.


It's interesting that if there is water in a settee, the pump can start when I step on board as the hull heels ever so slightly.  I never thought this design would be this sensitive.  I'm pleasantly surprised with how quickly it can empty the settee bilge though, especially when I sit on a gun whale to induce a heel.  A lot quicker than any scoop or sponge I can shove down there and not messy.  Both are benefits I never thought of.

CAUTION - You should occasionally verify the performance to your pumps to confirm functionality.  My bilge has been dry since I sealed the toe rail but I was surprised to discover debris plugging the barbed end of the thru-hull fitting at the cockpit.  This was construction debris that went through the pump and hoses only to be stopped at the square back side of the barbed end.  A good reason to vacuum the bilge clean after installation work.

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