Preview: How to Wire a Bilge Pump – Marine Electrical Systems

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Figuring out how to wire a bilge pump to your battery doesn’t have to be a chore to put off any longer. Follow Don Eley as he takes us step by step through the process and get some pretty handy tips along the way.

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15 Responses So Far to “How to Wire a Bilge Pump – Marine Electrical Systems

  • Drew Britten

    Drew Britten says:

    Great video Don! I would like to set something similar up for my Caledonia Yawl. I purchased a Whale Supersub Smart 650, given the small amount of space under my floorboards. One thing you didn’t mention in your video is battery capacity. If my pump specifies a 5A fuse, how many Ah do I need for day sailing and the occasional 3-day beach camping trip?

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      Don Eley says:

      On small boats, like your Caledonia, I typically install a small 32 Ah AGM battery like the Deka 8AU1H. If the boat isn’t leaking badly and not encountering any constant heavy rain, it should be able to go a month or two between charges. The pump probably draws less than 5 amps so you should get 4 – 6 hours of run time out of the battery. That’s a lot of bilge pumping.

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    John Simlett says:

    I have to tell you that I’ve just wired my new-build using this series by Don. I went from total novice to having installed, bilge pump through to sonar and GPS just from watching this series. AND I didn’t electrocute myself or set fire to the boat in the process. Massive thanks to Don and the team at OCH!!

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      Don Eley says:

      Thanks so much for the positive comments on video series and I’m glad to hear they were helpful.
      All the best,

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    Karl Seidenberg says:

    What design is the gorgeous boat in the background?

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    Bob Lister says:

    I have an uncovered boat that lives on a mooring also. I had a float switch fail and almost sank the boat. I have since switched to a water sensing pump that cycles every two minutes. I was sceptical at first but have had no low battery problems after two years of use. I also like to put a bit of dielectric grease on all connections to prevent corrosion and make plugs easier to disconnect.

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    Al Velieri says:

    i am in the process of wiring boat as we speak..your videos have been of great assistance. my only question would be is it better to crimp or solder?

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      Jerry Wegman says:

      My non-expert understanding is that on a boat crimping is better, because soldering creates a hard spot and then vibration is more likely to break the strands of the copper wire.

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    John Hughes says:

    My only critique of this video is that when you’re tightening the nut on the battery terminal, you haven’t covered up the other terminal.

    If you happen to drop that box-end wrench across the two terminals, things can get ugly in a hurry. Maybe the wrench you’re using is short enough that it can’t bridge the terminals, but if not .. then it’s worth the time to place even a scrap of cardboard over the other terminal while you work. I once dropped a 12″ crescent wrench when working above a battery, and it managed to short the battery in the course of bouncing off it. Sure made a big noise for a moment. There’s a burned out little hole and some black char on the handle-end to remind me not to do that again.If it had rested on the terminals, I expect it would have gotten VERY hot, and the battery might have exploded.

    As for “fancy strippers”, Radio Shack sells something they call “Heavy-Duty Automatic Wire Cutter/Stripper” for about eighteen dollars. Harbor Freight has an essentially identical tool for eleven. I used one to rewire my whole boat panel (about 30 circuits), and that tool is now a permanent resident of my electrics box, along with the Ancor crimper I bought years ago. Nowadays I might buy a cheap knockoff crimper at Harbor Freight, but I hate re-doing electrics, so maybe I’d pay the Ancor price at Defender. Just about everything I’ve ever crimped with the cheap crimper/stripper has eventually failed, while almost none of the connections made with a good crimper have. The other three essential tools in the box: a cheap volt-ohm-amp meter, a soldering iron/solder, and a butane lighter, for those times when I have to heat-shrink something and don’t have a 110V outlet for a heat-gun.

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    Don Eley says:

    Thanks for your comments on the bilge pump installation. The outlet of the pump runs under the floor boards forward then makes a loop up just under the deck and then to a thru-hull fitting at the boot top about 6″ above the waterline. The loop prevents any back siphoning regardless of the angle of heal. This installation has worked great for taking care of rain water and I usually only need to charge the battery once during the summer.

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    Peter Carleen says:

    Thanks for the nice little how-to video. The pictorial details of the beautiful interior of the 12 ½ are a nice bonus.

    I set up a very similar system a couple years ago on my Caledonia, which lives all summer on a mooring. The nice mooring cover that that I got with the boat has, after 12 years, shrunk a bit, and although it still can be made to work, it takes a bit of time to deploy it, so I generally leave the boat open and rely on the bilge pump to keep the rain from filling it up. The cover is great to protect the sails, though.

    Those fancy strippers and crimpers are great if you do this kind of work a lot, but I’m glad you demo’d the cheap stripper/crimper that most of us have. That worked fine for me. I will have to locate one of those nifty inline fuse holders you use, to replace my humbler version.

    You didn’t mention how the tubing is routed. Do you pump out over the gunwale? A temporary set up? Certainly we don’t want to undermine the classic look of this girl!


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