The topic of bilge pumps came up after taking a couple of trips on different boats down to Antigua and visiting on friend’s boats, such as Second Storm, a well-maintained Hallberg-Rassy 53 apportioned with the mindset of a functioning offshore sailboat. The ARC (Atlantic Rally for Cruisers) requires boats to have at least two functional, independent bilge pump systems: One manual pump, and a second manual or electric pump. A high-capacity pump (minimum 200 liters/minute or ~3,000 GPH) is mandatory for emergency use.
Skyward came with one 2,000 GPH bilge pump that connects to the port side cockpit drain and a manual pump operable from inside the cabin which pumps overboard just a few inches above the waterline. The 2000 GPH pump and the manual pump suction are shoved down into the deepest part of the bilge. There isn’t much room down there for more ‘stuff’. But since we wanted to align more closely with the ARC and World Cruising Club (WCC) requirements and generally increase our ability to deal with a leak, we decided to find a way to add a new emergency bilge pump.
For me, everything starts with a hand sketch and talking it over with friends and the Admiral. I didn’t want to stack the new large bilge pump on top of the 2,000 GPH pump, and that meant that the large bilge pump would be on the shoulder of the bilge. It wouldn’t make sense to go through the trouble to install an emergency bilge pump just below the cabin floor, and so thtere is a balance of being too high to be worthwhile, and the inconvenience of squeezing the new pump into a spot that is too challenging to access or event construct.
Looking at previous installations and asking around the HR forums, I decided to route the new discharge line to port which gave me orientation. As you can see in the picture. After specifying the emergency bilge pump to be a Rule 4,000 GPH model, the next step was to determine the best way to mount it ot the shoulder. The challenge was the curved surface. I picked up a 1/2″ sheet of structural FRP from McMaster-Carr, and epoxied a few together to create a 1.5″ thick puck. Then I carved it to the approximate shape of the shoulder of the bilge to increase fitment. Finally, I bedded it onto a layer of WestMarine Six10 thickened expoxy.
Next step involved cutting a hole in the side of the boat for the discharge thruhull. The pump has a 2″ discharge, and I decided to reduce that down to 1.5″ for many reasons primarily being the practicality of sourcing an acceptable hose and secondarily being the challenge we would face routing a 2″ house. I decided to go with a vented loop design and a stainless steel ball valve connected to the 1.5″ stainless steel thruhull. After dry fitting pieces together and eyeballing and measuring, I marked the spot on the inside of the boat where the hold needed to be. I grabbed my Milwaukee 2″ hole saw bit, and went to work from the inside first.
Mistakes were made. We fixed them, but we now have a 1.5″ hole drilled about 26-28 inches above the water line. I applied thickened Six10 epoxy to the core of the hole. The sandwiched hull consists of 8-9mm of laminate fiberglass on the inside, 20mm of solid foam core, and 12mm of laminate fiberglass on the outside to give a total of approximately 40mm thickness. We applied 4200 to the thruhull and all fittings to get everything set exactly where we wanted it. I didn’t put the thruhull up against any backing plate which may eventually need to be re-considered. I routed the 1.5″ hose under the cabinets and floorboards and made the connection to the 2″ discharge hose. Note in the 1st picture, the horizontal blue tape is the approximate water line.
To finish the initial system design, I installed a Rule Eco Switch under the galley cabinet frame and a Rule Rocker Panel Switch above the engine room door. I connected all wiring to a 4 circuit terminal block inside a Newmar PX-1 waterproof junction box to ensure all connections can be easily removed in case the pump needed to be fully changed out in the future.
The engineering design of this first phase of installation is shown in the diagram below. In commissioning this install, the pump turned on right away when in manual. I tested the Eco Switch by setting the Rule Rocker Switch to Auto and then removing the hose from the base of the bilge pump and gently blowing into it. In a subsequent phase of design and installation, I will install a switch at the helm to override the rocker switch and force the emergency bilge pump to activate as well as adding a high water alarm.
Because of the installation, I have about 6 feet of elevation as well as a reduction from 2″ to 1.5″, about 20 feet of 1.5″ hose, as well as a 45″ NPT-to-hose barb fitting, a full-flow ball valve and a sweep elbow. All of those features cause the pump to have to work harder to achieve flow. Not to get into fluid dynamics and detailed flow calculations looking at coefficients of friction and associated headloss, I roughly expect the pump to operate around 3,000 GPH.
Overall, I spent around $1200 not including Six10, epoxy resin, bilgekote, 4200 and screws/nuts/washers that I either had or needed to pick up. An alternative was to purchase a similar-sized dewatering pump from McMaster-Carr. Depending on the specification, I would have spent anywhere from $700 to $1,000 for a pump and then additional monies for hoses and fittings. That approach would also draw power from an inverter whereas the fixed 12V installation I just completed draws power directly from my starter batteries which are 220 Amp-hr rated and probably 110 Amp-hr realistic capacity based on a 50% usage factor.
I like the fixed installation because it takes the worry away about the reliance on another system to ensure the boat gets pumped down. It seems to be much more common on boats set up for overseas trips to have a fixed emergency pump installed. We enjoyed this phase of the project even more when it was complete! It was a lot of work to route the discharge line and stressful to cut a hole in the side of the boat.
The Loxodograph 