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Pin holes in aluminum bottom

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  • Pin holes in aluminum bottom

    I have been confident in my 1987 221 islander restoration so far. I have removed the transom, decks, and all of the flotation foam. The foam was water logged in the bow, near the gas tank, and the transom area. I pressure washed and acid etched the inside of the hull. While I was under the boat drilling out a few rivets I noticed some small blistering in the bottom paint. After scraping off the blistered paint I discovered 6 pin holes. About 1/16 to 1/8 in diameter. From the inside of the boat these pin holes were undetectable. Now I am not so confident. What caused this? Will it continue if so how do I stop it? What is the best way to make a repair? Help Please.

  • #2
    below are a number of reasons for pin-holes. they are caused by galvanic corrosion

    someone replaced bunk boards on the trailer with treated lumber
    someone boats in salt water and the carpet on bunks retains salt-water against the hull
    someone used the boat as a ground for something electrical.

    if it is just the 6, clean the area, drill out to a larger size, install a rivet with some 5200
    Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

    1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

    Past Boats
    1970 Wooster Hellion - Merc 9.8
    2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
    1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

    What’s behind you doesn’t matter.Enzo Ferrari

    Comment


    • #3
      Thanks again Cheesehead, you have been a great help in my project. The holes are in the area of the gas tank filler hose, below water line. As far as I know the boat has never been in salt water. The PO had a make shift 120 volt power inverter system with 4 home style outlets and a string of rope lights. The anode was painted over. Hopefully drilling them out will get into some solid metal.

      Comment


      • #4
        After I cleaned it better with an abrasive wheel, it’s worse than it looked. 2 sections (between 2 ribs) are deeply pitted and several more holes have showed up. Some around rivets and under ribs. I am thinking about patching in two large pieces of aluminum from the inside. Will this work. Or gas welding the pitted areas. Or maybe glassing the inside.

        Comment


        • #5
          with a riveted boat, there is a sealant material between the outer hull sections that are riveted together that makes welding difficult.

          my guess something was wired wrong with the power inverter, etc. and you have a lot more galvanic corrosion elsewhere.
          Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

          1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

          Past Boats
          1970 Wooster Hellion - Merc 9.8
          2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
          1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

          What’s behind you doesn’t matter.Enzo Ferrari

          Comment


          • #6
            Do you think glassing or riveting in sandwich type patches will work?

            Comment


            • #7
              glassing wont work

              post pics of the corrosion so we can see what you are working with
              Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

              1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

              Past Boats
              1970 Wooster Hellion - Merc 9.8
              2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
              1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

              What’s behind you doesn’t matter.Enzo Ferrari

              Comment


              • #8

                Comment


                • #9
                  I have circled the worst of the corroded areas. Note how the corrosion May be under rib #7. The problem area is in between rib #6 and #8 worst in the port side and progressively better as it goes down to center line and up the starboard side. Note I numbered the ribs from the transom forward. #6-#8 are about midship under the gas tank. Oh. I have also found some minor pitting inside the gas tank directly under the sending unit.

                  Comment


                  • #10
                    I would consider grit-blasting the whole surface and coating with one of the enecon flexiclad products.

                    https://www.enecon.com/products#
                    Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

                    1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

                    Past Boats
                    1970 Wooster Hellion - Merc 9.8
                    2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
                    1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

                    What’s behind you doesn’t matter.Enzo Ferrari

                    Comment


                    • #11
                      Thanks for that suggestion. It looks like I should remove the #7 rib to make repairs underneath and then re rivet it back in place.

                      Comment


                      • #12
                        Back to square one. Those products are cost prohibitive. Smallest amount shipped is over $700.

                        Comment


                        • #13
                          Sign up today
                          you dont want to ship the products, you then have to pay the EPA fees. find the local distributor

                          you can try gluvit http://marinetex.com/products/marine...oducts/gluvit/

                          its about $40
                          Cheesehead boating the Gulf Coast of FLA 27.51° N, 82.53° W

                          1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - https://forums.iboats.com/forum/owner...988-rogue-2420

                          Past Boats
                          1970 Wooster Hellion - Merc 9.8
                          2002 SeaRay 190BR - 5.0 - A1G2 - "Cheeseheads in Paradise"
                          1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

                          What’s behind you doesn’t matter.Enzo Ferrari

                          Comment

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