Water below the floor

Discussion in 'Boat Design' started by Super165, May 24, 2008.

  1. Super165
    Joined: May 2008
    Posts: 1
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    Location: Tulsa

    Super165 New Member

    Hi all,

    I recently purchased an 87 Ski Supreme and have just discovered when I jerk the boat around on the trailer, what sounds as water below the floor, in the stringer area. I removed a screw and ran a small hose down the hole - and siphoned out a lot of water, but there is still what sounds to be a lot more remaining.

    I don't know how long the water has been in there, but the floor is rock solid and just tapping on the stringers, they sound solid too - making a uinform sound up and down the length.

    Anyone have any ideas, as to how I can get the water out?? As of right now, I am thinking of removing the fuel tank and drilling some 1" holes in the floor, so I can run a big enough hose to get all the water out I can, then patching the holes back up. Any other ideas?

    Thanks for any help.

  2. tom28571
    Joined: Dec 2001
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    Location: Oriental, NC

    tom28571 Senior Member

    I once bought a motor boat and later found the same problem. My boat had a small well at the transom where a bilge pump and drain plug through the transom were located. I got a long drill bit and went in through the transom drain to make a hole in the forward end of the well. By recording the number of 5 gallon buckets of water I got, I found that there had been 500 pounds of water in the double bottom. Maybe you can do the same if there is a well or drain depression there. Probably most such boats will have gear mounted to the cockpit sole with screws and not properly sealed. That was the problem in my case.

    Over a long period of time, even small leaks are enough to let lots of water in. My boat handled much better and was easier to launch and retrieve after getting all that extra weight out.
  3. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    This is a common problem with many types of boats. The structural grid, below the sole is sealed in and not provided any weeps to let water drain aft and worse, not access to the sump or drain plug. In most cases this results in soaked floatation foam, rotted structural elements (stringers, sole supports, etc.) and a bunch of extra weight the boat has to drag along.

    The soaked foam isn't removable without removing the sole or at least large portions of it. This foam can hold many hundreds of pounds of water. It doesn't just drain out and stays in the foam for many months even if exposed but under roof. The best course is to remove it.

    If your stringers and sole are okay, just patch up the seams, after providing some weeps to let the moisture drain aft, plus provide access to the sump (where the pump lives), so it can exit the hull when you park it on the trailer.

    On a few occasions I seen folks who have drilled many holes through the bottom of the boat to let the water drain, then counter sunk them a bit and sealed them up with a dollop of epoxy (ground flush when cured). This will get the water out, but doesn't address the foam or the potential for moisture damage to the other structural elements.

    Walk around the sole in the cockpit, checking for soft or spongy areas. If any (likely on a 20 year old boat), then you have rot in the supports and possible stringers and the sole has to come up for repairs. Check prevoius threads on these subjects, there's lots of information about them.

  4. alan white
    Joined: Mar 2007
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    Location: maine

    alan white Senior Member

    PAR is right on. It's a shame so many boats have no gravity drainage to the sump, depending entirely on the kind of waterproofness found only in near new boats of that construction. That sealed area will always attract water and eventually the boat will be destroyed.
    Once into the area, it's common to find out that the water has done a job on the stringers and underside of the cockpit sole.
    In repairing it, it makes sense (if the boat is worth the effort to you) to rebuild the framing and then provide a means for all water to flow aft to the sump area ahead of the engine.
    Fiberglass boats, if not hit by blistering, can last a long time, but only if the wood that stiffens them is intact.

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