Bilge sumps for multiple pumps ??

Discussion in 'Boat Design' started by Bullshipper, Jun 21, 2008.

  1. Bullshipper
    Joined: May 2008
    Posts: 106
    Likes: 2, Points: 18, Legacy Rep: 21
    Location: Mexico

    Bullshipper Bullshipper

    I am looking for a bilge setup where one 2" pickup feeds a sump where a lot of small livewell pumps can be installed to feed multiple livewells and tuna tubes.

    The idea is to make only one perforation in the hull to reduce drag and then perforate the sump lid with up to 8 pumps.

    Does anone know of a boat that is set up this way, and a link with pictures.

    Fiberglass examples are great. This is an alloy application.
  2. kmorin
    Joined: Apr 2005
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    Location: Alaska

    kmorin Senior Member

    Seachest by any other name?

    Bull, I may not understand your description but is sounds like a pretty typical sea chest.

    If a single 2" riser is welded to the hull as the through-hull, plate doubled and gusseted and topped by your preferred valve as the seacock; then you can just T and branch-T until your heart's content with 1/2" lines off that pipe riser.

    If you prefer to weld a small manifold/sea chest then use a 2" or 3" pipe that is 6-12" long and weld flat plate ends in that and line the top and bottom with halves of 6061 T-6 NPT (fem) couplers of 1/2" pipe welded (I'd say TIG was the best for this application) to the round of the 2"-3". This will give you a sump/manifold/seachest with a line of female pipe fittings along the 12:00 and 6:00 axis of that short pipe and a supply in one end or through fitting in the opposite end. Such a manifold will flood from the through-hull riser above the seacock, and you'd mount the smaller valves for each of the pump suction lines for all of your individual tanks above and below, if oriented horizontally, this sea chest/manifold stubbed out in hose barbs. If you mount the seachest vertically then your valves would lay side to side.

    If the top of your seacock is flanged then you could flange the seachest instead of flat plating one end. If the top of the seacock is threaded you could use a 2" thread fitting on the end of the seachest. If you have other flow through this same 2" riser (?) then T to other flows and use the remaining side of that T for your seachest supply to the live well pumps.

    This should do the trick pretty simply, these are used on fuel headers, tank supply/return manifolds, through-hulls for multiple cooling supplies and various other applications.

    I'm not sure if this helps any? I'm not aware there is any drag on a hull opening unless there's a scoop, but I do agree keeping the through hull's to a minimum is good practice.

  3. marshmat
    Joined: Apr 2005
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    Location: Ontario

    marshmat Senior Member

    Offshore folks call this setup a "sea chest" and the better ones use this concept for just about everything that needs raw water. Much cleaner and safer than having 20 seacocks sticking out every which way. It also has the distinct advantage that your intakes work equally well at all boat speeds.

    A solution like this would be remarkably easy to implement in your application (I think you're talking aluminum?) Simply build a rectangular box large enough to fit all your intakes around the edges. The box can be welded but the lid should be bolt-on so you can clean it out if anything clogs up. Get one big, beefy seacock of sufficient diameter to handle the flow of all the pumps together and mount it in the hull. (Note that a valve screwed onto a through-hull is not the same as a real seacock- one will break off and flood your bilges with seawater, the other won't.) Run a short piece of pipe from that intake to your box and mount the thing securely in your bilge. No two applications are identical, but the concept is the same and as long as each individual pump's intake is below the boat's rest waterline they should all self-prime just fine.

    edit - so kmorin and I posted the same suggestion at about the same time, he suggests piping while I suggest a box- same concept, either will suit you just fine depending on what style you're more comfortable fabricating.

  4. Bullshipper
    Joined: May 2008
    Posts: 106
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    Location: Mexico

    Bullshipper Bullshipper

    Thanks a lot.

    Sea Chest ws the name I was looking for.

    The pipe with a threaded cap for a cleanout seems like it would be the optimum setup.

    I assume I also need a vent pipe/hose to eliminate air as livewell pumps airlock pretty easy.

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