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Tracking down a (saltwater) leak

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  • Tracking down a (saltwater) leak

    Albeit it's not a classic, there's a wealth of knowledge on this forum which may help me track down my issue for my '98 191. The hull is wet slipped and any water that accumulates in the bilge, dockside, is freshwater from wash downs and rain (I know those culprits). However, after running the boat, saltwater accumulates in the bilge. The seacock for my livewell pump is always kept closed, and my deck plates near the transom have recently been replaced and lids resealed, along with new scuppers. The saltwater intrusion does not appear to be coming from on the deck. Any insight as to where this water may be coming from?

  • #2
    While the boat is on the trailer, run water under pressure (not a lot of pressure) and listen below deck for water dripping into the hull. The PVC drain tubing can crack and allow entry whille the boat is in the slip.
    Also, check around the gunnel for water entering between the rubrail and the hull along the bottom of the rail. The gunnel cap is fastened to the hull with screws through the rubrail. Over the years the screws can strip out of the hull due to contact with piles and bulkheads. Wash coming up the hull in rough seas can enter this gap...small as it is.. Though small, I was suprised to find a good amount of water entered my hull this way. It was only noticable following a 2-3 hour roughs run off shore...but that little gap was the culprit.

    Good luck! Let us know what you find.

    Ole Joe
    Just floundering around
    White Hall & Ocean City, Maryland
    1978 Mako 25


    • #3
      It's not easy to determine if a leak is saltwater or fresh since there is almost always some salt in the bilge and any fresh water that meets it will dissolve some salt.
      Assuming the rate of water accumulation is small, it would help to determine if the water buildup in the bilge is constant over time or more event driven like after a run as mentioned or after a rain soaking. Water can get in from the outside in a few ways but the two most common are leaks from fittings below the water line or leaks from internal plumbing as could be the case for deck drain fittings. and scupper hoses/fittings.
      Leaks form hull fittings that you can get to are a lot easier to find. Just dry out everything you can and wait a while. hey go feel around for wetness. Note that anything that pierces the hull, even an engine bracket bolts or screws can leak if they are below the water line. The garboard drain is another area to check but often that is normally wet by nature and in that case you have to judge if the amount of water is increasing.
      You probably also can't tell how often your bilge pump is operating is it is operating at all.
      For thru hulls that are hard to get to, assume that they are probably below the water line if the leakage is steady and not more common after rain or a run.
      The key is to make and note frequent observations and external conditions and narrow down causes from that info.


      • #4
        agree with flounder on many points, i'd pull out of the water, drain hull, put drain plug back in and using a hose fill the bilge up with water, disconnect bilge pump wire to the battery, and yourself and if you can an extra set of eyes even better, get under the boat and see if you can see any water coming out from anywhere? That might tell you what you need to know? If not, any plastic fitting or cheap hose could be suspect. If you have only one bilge pump on the boat, add a 2nd


        • #5
          The problem with the filling of the bilge with water is that in order to create the same static pressure that the hull experiences when in the water, you have to fill the bilge to the same level as the outside water would be and that might be a lot of water and possible submerge things you don't want submerged. Granted a big enough leak would probably show up using the fill the bilge method but you would probably also see water leaking with the bilge empty and the boat in the water.
          As I stated earlier, try first to understand under what circumstances and/or events the bilges get water