Installing an Electric Bilge Pump

Written by Jason Learned on 23 March 2012. Posted in Gear & Outfitting

Getting knocked out of your boat and back in by yourself is hard enough, but once back in you have to hand pump all the water out, or do you? Having a reliable electric bilge pump to pump that water out will keep both of your hands on your paddle allowing you to brace in the conditions that knocked you over in the first place. It is also a handy toy that you can use to douse your unsuspecting friends with a cold blast of water.

An electric pump is a great piece of safety equipment especially if you find yourself paddling in dynamic waters but just like any other piece of equipment it can fail, so you should not get rid of your hand pump just yet or stop practicing your rolls. Training and practice should continue to be a part the central part of your paddling safety plan.

There are several good electric bilge pump plans published on the internet, the one I found most useful was at Gnarly Dog’s Blog. I started with this basic design and refined it to fit my NDK Romany Excel and to make it as simple and reliable as I could. This has taken several attempts and changes to attain these goals.

If you do not want to get your hands dirty or do not have the time, Blue Water Kayak Works sells the Freedom 500 Electric Bilge Pump Kit. The kit includes everything you need to install it yourself or if you live in the Puget Sound area you can have Rhonda Schwab at Kayakers Go Coastal install it professionally for you.

This article will hopefully illustrate the steps I took and the considerations I made when installing my pump thus giving you a big head start on your own project.

First thing I did was to sit down and take a look at my boat and see where I would place the parts. I was putting this pump into my NDK Romany Excel, which has the High Performance Seat, an angled bulkhead and no backrest. 

I chose the more challenging installation of placing the pump behind my seat and placing the battery box in my day hatch. I didn’t want the pump in front of my seat so I could keep the cockpit as clean as possible and I did not want the battery box exposed to the water in the cockpit. This created a couple of complications:

• First of which was there wasn’t enough room behind the seat for the pump, so I would need to modify the rear bulkhead to accommodate the pump.
• Secondly, I would have to drill a hole in the bulkhead to pass the wires through it to the battery box.

I drew up a basic plan on paper and came up with a parts list and began purchasing the pieces. I bought what I could find locally and then turned to the Internet to purchase the rest, ordering as many parts from the same vendor to reduce shipping costs. Once I had the pump in hand I began by modifying the rear bulkhead.

Modifying the Bulkhead

Tools/Supplies Used

1. 2oz Woven Fiberglass Cloth
2. Resin & Hardener
3. 1 Quart Paint Can (Form)
4. Working Board
5. Heavy Duty Plastic Wrap
6. Dremel W/Cutting Wheel and Multipurpose Cutting Bit
7. Plastic mixing containers with measuring lines
8. Cheap 2” paint brushes
9. Latex gloves

With the pump in hand, I could gauge how wide the cut out should be to accommodate the pump. I needed to find an object that that was similar in width that I could make a “U” shaped fiberglass form from. I found that 1 quart paint can turned out to make a great mold for this purpose.

I taped the can onto a piece of wood to keep it from rolling. I then used heavy duty plastic wrap as a non stick barrier over the can by draping the plastic wrap over the can and affixing the sides to the board making a "U" shaped form.

I then mixed up a batch of clear resin and using 2oz fiberglass weave cloth starting placing the weave down saturating it with resin and placing another layer of cloth down and saturating it again with more resin and began building up the layers to the same thickness of my bulkhead. I let this harden overnight. The next day I pulled the now hardened fiberglass shape from the form and cut off the rough fiberglass edges leaving a nearly perfect U shaped form.

Now came the nerve-racking part, cutting into the bulkhead. I was hoping I wasn’t about to ruin my new boat. I started by marking the center of the bulkhead with a felt tip marker. I then measured the width of the U shaped piece I had made and placed those marks on the bulkhead centered over the centerline. I then measured how high the form was and marked that on the bulkhead as well. I then drew in the vertical lines and free handed the round top where I though it should be.

I started cutting through the bulkhead using a Dremel tool staying well within the lines. I figured I could sand it down to fit more easily than trying to add more fiberglass. After a few test fits and cuts I got it close enough to be able to seat the "U" shaped piece into the opening. I trimmed off the excess from the top and with some sanding was able to get the piece to fit just perfect in the bulkhead. Now all that was left was to glass in the new piece using resin and 2oz glass cloth. I put 2 layers on both the front and back and let it dry over night.

Making the Magnetic Switch

The following parts are needed to make the magnetic switch.

1. Magnetic Reed Switch
2. Hard tubing for a form
3. Marine Grade Wire (Don’t skimp here, trust me use MARINE grade wire)
4. Zip Ties
5. 1/8” Closed Cell Foam
6. 1” Closed Cell Foam
7. 1/8” Shrink Wrap

Tools Needed

1. Soldering Iron
2. Rosin Core 60/40 Soldering Wire
3. Razor Knife
4. Rubber Cement
5. Resin/Hardener
6. Plastic mixing containers with measuring lines
7. Tape
8. Latex gloves

I went with a magnetic reed style switch, as it seemed to be less prone to saltwater intrusion and corrosion.  While more complicated than a toggle switch, there are no exposed or moving parts to corrode or break. I used Gnarly Dogs directions for making the switch except that I used a larger magnetic reed switch so I could eliminate the use of a relay in the battery box.

I figured I would mount the reed switch directly under the bungee cord nearest the cockpit, near the peak of the neck. This would allow me to mount the magnet on the bungee cord. To activate the pump, I would just need to slide the magnet over the switch and voila the pump turns on.

I cut 2 equal length pieces of 16 AWG Marine Grade Wire long enough to reach from the switches location in the cockpit to the battery box in my day hatch and added a few feet just in case. I used 16 AWG wire because it is the same size that came on the pump. You have to solder the wire onto the ends of the reed switch and carefully bend one of the leads back over the switch. You must take care when doing this so you do not accidently break the glass ampule. Since these were so cheap I bought a few extra just in case.

The next step was to make molds for the switch and magnet. The made the mold for the switch out of a piece of scrap PEX tubing I had lying around, but any tubing with a sufficient diameter to encase the switch will do. For the magnet I used a nylon garden house cap.

I cut the PEX tubing long enough to extend past the switch on each side by a ½ inch or so and I capped one end with tape. I filled half of the tube with a batch of resin and then placed the switch down into the tube trying to center the switch in the tube and filled the remainder of the tube with more resin and taped the switch in place.  Once the resin hardens the switch is completely encapsulated and is protected from the elements.  I left the PEX tubing surrounding the resin-encased switch for extra bump protection. Originally I cut the tube in half the long way as gnarly dog did but found the resin to be too flexible when fully cured leaving the glass reed switch susceptible to breakage.

Before the leftover resin started to cure I took the garden hose cap and filled it about 2/3 full and left it to cure. I would come back later to add the magnet and encase it in more resin.

With the switch fully cured, I needed to make a protective foam enclosure for the switch that I could use to glue it to the underside of my foredeck. I cut a small rectangular block out of some scrap 1” thick foam and cut a notch in it to fit the switch and glued the whole thing under my foredeck directly under the bungee cord.

I then ran the wires out of the way of my knees and over to the discharge hose securing them to the underside of my foredeck by gluing a strip of the 1/8’ foam over the wires. The wires were then zip tied along the hose all the way back to the back bulkhead until I reached the pump wires.

All four wires at this point were wrapped together using ¼” shrink wrap tubing extending long enough to pass through the bulkhead and all the way into the battery box. I used Ancor, Marine Grade, Electrical Wire Seals (Round Cable, 18 to 10-Gauge, 3/8-Inch NPT) as the watertight through hull fittings on the bulkhead and battery box.

The last thing to do was to finish the magnet holder. I mixed another small batch of resin and placed the magnet inside the garden hose cap from before and poured the resin over the magnet and filled the hose cap until the resin just bulges above the cap. Once the resin fully hardened, I drilled a hole large enough to thread my bungee cord through being careful to miss the magnet. Lastly I sanded and polished the resin so it was flush with the cap.

Later on, once the system was all hooked up and running I added a small black zip tie to the bungy cord as a stop mark for the magnet. This made it easier to operate in rough water.

Pump Installation

The following parts are needed for the installation of the pump system.

1. Pump
2. Discharge Hose
3. 2 Stainless Steel Hose Clamps
4. 90° Discharge Elbow
5. 1/8” Foam
6. Ancor 765000 Marine Grade Electrical Wire Seal

Tools Needed

1. Drill & Bits
2. Flat Head Screw Driver
3. Razor Knife
4. Silicone Sealant
5. Hack Saw

Pump installation is fairly straightforward and simple. You should start by choosing a location for the discharge port and where you want your wires to pass through the rear bulkhead and into the Day Hatch. There are a couple of things to keep in mind when choosing these locations. Your discharge port should be located somewhere to keep the hose and fittings out of the way of your feet and legs.

If you have a vertical rear bulkhead you may be able to install it behind you, but keep in mind the stream may end up showering down on in and your cockpit. Boats with an angled bulkhead like mine, installing the discharge port on the rear deck is not an option without passing the discharge hose through the rear bulkhead into your day hatch, which presents all sorts of problems if the hose becomes detached in your day hatch.

I chose to install the discharge port on my foredeck just aft of my forward bulkhead. Here the deck is angled out so the stream discharges over the starboard side of the boat. In REALLY windy conditions when I am facing into the wind this positioning does cause some spray to get in my face. Another option is to install it at the seam on the side of the boat but I decided against this because I did not want to scrape it off against the rocks while playing in the rock gardens. 

While I am talking about the discharge port, several people have asked how I keep water from coming in through my discharge port and filling up my boat. Simply put I don’t worry about it. The opening is so small that the amount of water coming in is really very inconsequential, besides I have an electric pump to pump it out! If you are still worried about incoming water through the discharge port you can purchase an inline one-way valve. I chose not to install this valve as this just adds another layer of possible equipment failure or malfunction. Others have used stoppers or plugs on the discharge port but again what do you do when this plug gets stuck and you can’t operate your pump.

Getting off my soapbox and back to the install. Locate where you want the discharge port to be and use a grease pencil to mark where you will be drilling. Make sure to account for enough room underneath for the tubing and clamp and your foot/leg position. To drill through the fiberglass with the least amount of chipping lay down a layer of blue painters tape over the area where you will be drilling through and use a sharp bit. This should minimize any chipping around the edges.  You will want to drill a hole only large enough to allow the fitting to pass through (usually a 1” hole for the ¾” elbow), read the instructions supplied with your fitting for the correct size hole.

With the hole drilled, I installed the discharge port and ran the hose to the pump next. I started by attaching the hose to the discharge port using the hose clamps. The 90º fittings have 2 screw on flanges to allow you to adjust the depth of the fitting. I screwed on the lower flange to bring the hose as close to the under deck as possible to ensure it stayed away from my big feet.  I then put a large bead of silicone around the threads at this flange and passed the threaded end up through the hole and screwed on the upper flange until the fitting was secure making sure the 90º bend in the fitting was pointing towards the stern of the boat. I then wiped off the extruded silicone sealant from around the fitting. Next I cut off the extra bit of threaded pipe extending up from the top flange using a hack saw and sanded the edges of the port smooth. I used a hack saw because the teeth were the smallest out of the saws I had on hand thus giving me a cleaner cut.

I found my stream to be breaking up and spraying all over the place instead of a nice solid stream of water. I always thought it was because of rough edges around the port but when I looked closely with a flashlight I found slivers of plastics from the molding process down inside the port at the bend. Once I had cleared those away I had a nice strong solid stream of water.

With the discharge port secured in place, I brought the hose back to the pump and cut it to the correct length ensuring I had enough to make the bends around the seat and clear my legs. I then attached the hose to the pump using another hose clamp.

Now was a good time to zip-tie the wires from the switch to the discharge hose, as I would be gluing the hose in place next with pieces of foam. I used several 2” x 6” strips of 1/8” thick foam to secure the hose in the exact location I wanted to alongside the hull in the cockpit.

If you are going to have the battery box in your day hatch you will need to select a spot on the rear bulkhead where you want all of your wires to pass through. I chose a spot 3/4 of the way up the bulkhead figuring when the boat is upside down little water should reach that location and right side up it should not be covered for very long. The hole size will depend on what you end up using for your through hull fitting. I used the Ancor 13-10 Marine Grade Wire Seal so I drilled a 5/8” hole and sealed it using silicone sealant.

Other places to locate the battery box are to mount it on your front bulkhead with a couple of Velcro straps or another option is to mount your pump in front of your seat and place the battery box behind your seat.

The wires from the switch and the pump came together behind the seat and I wrapped all four wires together using ¼” shrink wrapping. I used bulk length shrink-wrapping so that I was able to wrap the wires all the way into the battery box to reduce any amount of water intruding between the wires and it looks clean and professional. As an added measure of security I added a small amount of silicone sealant to the backside of the wire seal.

The only left to do now is wire it all together in the battery box.

The Battery Box

The following parts are needed for the battery box build.

1. Otterbox 2500
2. Ancor 765000 Marine Grade Electrical Wire Seal
3. Inline Fuse Holder and 2 amp Fuse
4. Traxxass Parallel Battery Harness (optional)
5. Traxxass Battery Connectors
6. Weatherproof Butt Connectors

Tools Needed

1. Drill & 5/8” Bits
2. Wire Strippers
3. Wire Crimpers
4. Silicone Sealant

My pump is being driven by 2, 14.8v, 2600mah Li-Ion rechargeable batteries in parallel. The batteries come with bare wires so you have several options for connectors. I used Traxxas High Current Connectors. There are cheaper and easier alternatives such as the Standard Tamiya Connectors, but using wimpy connectors are like attaching a garden hose to a fire hydrant. The pressure is there but the flow is strangled with resistance.

The Traxxas connectors are also gold plated which means no corrosion if they get wet. The Traxxas connectors are installed by soldering the wires directly to the connectors, this creates a very reliable and strong connection. Both style connectors can be found at your local hobby shop or online. Directions for learning how to solder can be found online by doing a simple Google search.

In addition to the Traxxass connectors and batteries there are also a marine grade inline fuse and 2 splash proof butt connectors installed in the battery box. I also usually store a couple of extra fuses for backup. Others used a relay in their system to step down the current being passed through their switches so they don’t fry them. I used a larger switch that could handle the additional current, thus eliminating the need for a relay.

I have tried several different configurations with my battery box. At first, I wanted to be able to unplug the box from the boat and bring the whole thing into the house when not in use, however, I have not been able to find any suitable waterproof plugs that have stood up to saltwater intrusion.

To alleviate this problem and make a bomber dependable waterproof battery box I went with a simple wire seal. All of the wires are passed into the battery box through the wire seal and covered in silicone sealant for good measure. All of the wire connections are then done inside the box. There are no wire connections exposed to water anywhere in the system. I have been using it this way since 2011 without any complications.

Materials List

Download pdf verison57.83 KB

List last update Mar 22 2012

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