Saturday, October 9, 2010

Lazy or . . . It Just Makes Damn Good Sense?

After some research I decided to devise/install an electric bilge pump on my kayak. The first question most people as is "Why? Isn't the hand held model good enough?" I thought it was until I looked into the electric version.


  • An electro/mechanical system is open to failure due the very nature of the setup - electrical components in a marine environment.
  • Battery drainage. A battery has a finite amount of life.
  • Weight.  The total system is about 5.00 lbs and takes up a certain amount of room in the boat.
  • The location of the outlet will spray in your face if you try a paddle float rescue while the pump is running.


  • Requires no manual work from the paddler. Flip a switch and away she goes. Which means you can reenter your water-laden boat. Put on your spray skirt. Flip the switch and as you paddle, the boat automatically empties itself. In other words, no vulnerable downtime as you sit there with your skirt down (oo la la) trying to pump out your boat!!   Estimated times to empty a boat is 2-3 minutes - not bad!!
  • While it's electric, it's well protected from the water. In my setup the pump is the only part of the system that is in direct contact with any water. As the pump is designed for immersion, that is no issue - even as it sits in the cockpit. For double protection, the battery/electronics are house in a waterproof  Pelican case PLUS they are in the day hatch.  The switch is a non-conventional "jobbie" that I gleaned from Gnarlydog's blog. It's entirely impervious to water and there are no electrical components exposed to any elements. The "switch" on the rear deck bungee is unobtrusive as well, i.e, will not get hooked during scrambles or other rescue exercises. 
  • My battery is 4ah which means it should run the pump for about 1. 5 HOURS. @ 500 GPH. If you do the math, that's about 750 gallons of water. If I have to pump out 750 gal of water from my boat manually, then what's the point in even trying?!!

All precautions have been taken to mitigate the problems associated with electronics in a marine environment.  Battery and relay are in a watertight box in the day hatch. The reed switch is totally encased in epoxy. Pump is, by manufacture, completely sealed.

Battery life: If you need to pump for more than 1.5 hrs then you'd better rethink  your position.

A bag of sugar is about the same weight and size of the whole package (pump and battery pack). If you can't find room for a bag of sugar in your boat, then  . . . .?

As the pump may fail or the battery may die, a hand pump will always he stowed on board as well.


Pump 500 GPH Johnson- 20.00
Battery Single Lead Acid (SLA) 12 volt  4   ah -  Free (already on hand)
Reed switch 6.00
Relay  10.00
Pelican case - Free (first prize in Safety Race)
Check Valve:  7.00
Suction cups: 15.00
Thru-full fitting: 3.00
Fuse/holder:  4.00
Misc fittings and sundry items: 20.00


I'll admit that I relied heavily on the ideas of others to complete this project. I referred to Gnarlydog's blog entry quite extensively. 

In order to use the Pelican box I already had, I needed to remove the rubber liner so that the battery could fit, When you remove the liner you also remove the rubber seal. I had to make another seal out of neoprene I had lying around. It is self adhesive so I just cut a thin strip and set it around the lip of the box. Voila!!!

Waterproof testing the Pelican box.

One of the big problems experienced by others is the corroding of switches. Even waterproof ones had a habit of dying after a time in the marine environment. I decided to go with the magnetic switch. It simply required a reed switch (6.00) and magnetic "button" made out of a chair leg cap and a pair of rare earth magnets.

A reed switch is a tiny switch that relies on magnetism to activate it. The magnet moves the small reed inside and closes the circuit.  The trick is to encase the switch in epoxy to make it waterproof. I took a piece of rubber tubing cut down the middle. I placed the switch in the tubing and poured in the epoxy. The naturally occurring flat spot on top is great when you have to affix the switch to underside of the deck.

Reed switch

Reed switch encased in epoxy.

A reed switch is not powerful enough to power the pump, so you need to put a relay into the mix.

Battery, fuse and relay wired in.

The magnetic button is simply a chair leg cap with rare earth magnets. To hold the magnets in place you need to pour epoxy in around them. I left the magnets just slightly below the surface of the epoxy to provide protection from the salt water.

Switch button prior to pouring in the epoxy.

As my back deck is very low and often awash, I was concerned that the outlet would let in a lot of water = very dangerous. I found a check valve at Canadian Tire, It was intended for larger pipes so I had to step down the size to fit my 3/4' tubing. This valve is very free flowing yet jams air/water tight once the flow reverses.

Check Valve and Thru-hull fitting

The matter of attaching the pump was dealt with by using a 3" suction cup. I drilled a hole in the side of the pump and used the bolt from the cup to hold the pump. I placed a rubber washer on the inside to ensure watertightness. The suction cup holds the pump tightly to the bulkhead behind my seat. My bulkheads are foam and were starting dent in from the suction so I took a piece of thick sheet plastic and Aquasealed it onto the bulkhead. It holds incredible well and will not move until you break the suction.

Pump and suction cup.

The wires from the pump must run through the bulkhead. Aquaseal around the wires makes for watertight seal.

Dry testing the fit.

I decided to put the outlet on the rear deck simply because I did not want to run a long hose to the foredeck AND I wanted the hose as short as possible simply to keep the flow at a maximum. I painted the thru-hull fitting black with a plastic-specific enamel.

Thru-hull fitting painted and in place.
Many others have placed the magnetic button on their foredeck. I decided to go with the rear deck  simply because there was a short bungy cord all ready to go and because it meant all the wiring could be contained within the day hatch. It's very easy to reach so that is not an issue.  I placed a small twist tie as a stop to prevent the button from going to far. The button is small and unobtrusive and will not get in the way of any rear deck entries.

The reed switch assembly is held in place below deck right underneath the bungy cord. I initially toyed with the idea of epoxying the switch in place. Then I contemplated using small bolts. I finally decided to go with Gorilla Tape to hold the switch in place. This stuff is tenacious and I think it will work out great. If the test fails, then I'll resort back to my original plans.

Magnetic button

The matter of attaching the battery box in place was as tricky as the switch. I was planning on using industrial strength velcro but the self adhesive would not adhere well to the hull. I thought of glueing on straps as well. I finally decided to try the suction cups again. They are bolted directly to the box.  The box is then attached to the bottom of the hull. It holds very well and is easy to remove once you break the suction.

Pelican box with suction cups.

After tinkering with this over several evenings (while the boat sat in my living room!!) I was finally ready to give it a whir. I filled the boat up with water to a level I figured would be the most left after a reentry and roll. Fired up and pump and away she went. It took 3 minutes to empty. A very solid column of water comes out of the outlet and not a high spray that I was anticipating. The low arc is great because it is much less likely to catch the wind and blow all over you. It also means that a paddle float rescue can be done without feeling like you're being hosed down!!

Pump in action.

The amount of water left in the boat when suction stopped was less than what you'd have with a hand pump!!

Amount of water left after pump out.

And the check valve prevented any water from re-entering the boat. Perfect!!

Check valve works great!

 All in all, I am very pleased with this setup. It is small, relatively light yet it packs quite a bit of pumping punch!! I 'm really looking forward to trying it out on the water and in rescue practice.


  1. Sean,
    nice variation to my original set up.
    I love the solution of using the suction cups to affix the pump and the battery box to the plastic kayak. Good thinking.
    Keep on eye on that switch behind the cockpit: some paddlers have activated the switch without noticing and draied the battery.
    4Ah is a massive battery.
    With typical use, mine at 1.2Ah lasts many outings (rescues) before needing recharging.
    Instead of removing the Pelican box lining completely you can just cut out the section you need and leave the rest to act as seal on the lid.
    Nice pictorial documentation.
    Thanks for posting.

  2. Gnarlydog: Thanks for the input and the original idea!! I've used suction cups several times previous on other kayak projects. My camera mount uses a 3" suction cup as well as my hand pump holder (Both are covered in previous blog entries)

    I'll keep an eye on the switch. If I find it a problem, I'll just move it to another location. That's one of the great advantages of using the Gorilla Tape - ease of removal!!

    I know a 4ah battery is big but it was free - ya can't beat that. If I find I really like this system yet would like to carry a lighter battery, I'll just swap it out!

    I was hoping to be able to cut the rubber liner on the box but the battery was so big that, even with the liner removed, it could not close tight enough to be watertight. The extra height of the neoprene made for a very snug fit and a totally watertight casing!! Again, just one of those little hiccups you don't expect!!


  3. Hi Sean,

    Thanks for the great info! I'm in the beginning stages of assembling parts for an electric pump system.

    The pump will be installed in my Baffin P2, and I'm wondering what type of glue/adhesive you used to secure the reed switch? Did the gorilla tape end up working, or did you have to try something else?



  4. David: I just went with the Gorilla Tape and it held up well. Granted I put a fair bit on but it's inside the day hatch so you could not see it. I did not try any adhesives for two reasons 1) it's hard to find anything that will stick well to the poly and 2) it's an awkward place to try and position and hold the switch while the adhesive set up. Like a lot of things, I often use Gorilla Tape as a temporary hold to test a setup but then I find that it works so well that I just leave it permanently!!

    Good luck,