My boat didn’t come with an electric bilge pump. Since I have an outboard, and the only original below the waterline thruhull was for the galley sink drain, and the rudder post sits above the waterline, I guess they decided it wasn’t needed. Since the ice chest and head / shower floor drain both empty into the bilge, it can fill up pretty quick on a hot summer weekend with melt water and if someone wants to rinse off in private. I really wanted to install an automatic electric pump to keep the water level in check as I have on more than one occasion gone out for a sail and forgotten to manually pump out the water first, and when heeled over the water spills out onto the cabin sole and makes a big mess.
Due to the small volume of water the bilge can hold, and some old rule of thumb that I heard somewhere long ago, a reasonably sized working pump (aka non emergency pump) should be able to pump out the entire bilge in under 2 minutes, and about 30 seconds or less at the level the auto float switch kicks in. Based on this, and the estimate that my bilge holds about 5 gallons, that means I only need a pump that can handle 2.5gal / min, or 150 gph (2.5*60). Since the smallest commonly available pump is 500 gph (at zero lift), I shouldn’t have a problem with this. I also didn’t want an old float style auto switch as they are too easy to jam. I picked the Rule Mate 500 because it contains an integrated electronic water sensing float switch (i.e. no moving parts), and is rated at 250 gph with a 3ft lift (exactly what I happen to have).
I didn’t want to drill holes and screw the base of the pump into the bilge as I didn’t know what was under there, and I didn’t want to take any chances of moisture penetration, so I cleaned the surfaces with acetone and put a small amount of epoxy on the removable base and epoxied in the bilge where I wanted it. It won’t be a super strong bond, but that’s not a bad thing if I ever need to remove the base for any reason.
Next I removed the floor boards and fed the bilge hose through an opening in the stringer where the shower drain comes out of, and through a hole I drilled on the other side, along with the 3 wires to power the pump. Then I drilled another set of holes and fed the hose into the corner of the compartment where I have a nearly direct route back to the head. The second hole is for the wires coming down from the electrical panel to the pump.
With the hose now under the lav sink, I made a 1 1/4″ to 3/4″ T reducer and T’d the bilge hose into the lav sink drain, which is correctly located 12″ above the waterline. The way everything fits the sink drain acts like a vented loop preventing siphoning, and eliminating the need for an extra thru hull. It isn’t exactly as most experts recommend but fitting things into a 27′ production boat sometimes demands compromises, and in the end I’ve achieved the same end goal of what they are trying to do, with the exception that the lav sink and bilge still share a thruhull.
Finally I ran the electrical wires from the panel down to the space under the floor board between the stringer and the compartment everything ran into, and soldered the ends of each wire (it was already tinned wire) to make for the best possible connection, and crimped each wire with heat shrink butt-splices, heat shrank them, and then wrapped everything in electrical tape to keep it organized.
To test everything I filled the bilge with water from the FW holding tank, one pot full at a time, and turned on the pump. The It was pumped to the lowest level possible by the pump in about 20 seconds and minimal back flow the hose after done, Perfect!
I forgot to take more pics, but here is one showing the pump, and where the hose and wires are connected, with the connections being in a separate compartment (once the floor is reinstalled) from the bilge.
UPDATE: With the new electrical panel installed, I have wired the bilge pump so that the Auto circuit is tied into a push button breaker that cannot be turned off, but in the event it pops can easily be reset (after fixing whatever caused it to pop of course). The push button breaker is powered any time the main battery switch is in an “on” position. Also on the panel is a momentary manual switch that is powered off the main breaker for the panel.