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    4788 Rubrail Leaks

    For a while I’ve had water coming in the port lasserette area next to the exhaust box. Initially I thought the exhaust box was leaking, but that was subsequently ruled out to be rainwater accumulation. Cockpit clears were also down, so the cockpit area was dry.

    Troubleshooting began by shaping a ridge of silicon about a foot forward of the transom corner (along the wood riser “wall” at rear of the battery boxes) to the side hull wall to try and isolate where the water was running in or down the hull walls. I also rammed paper towels up underneath the hull and lasserette wall joint, also along the hull horizontal ledge near the exhaust box, and up the gap in the back corner between the transom wall and the cockpit wall (2” gap near where the duckboard bolts come thru).

    Lots of rain discovered water water coming down the interior cockpit wall (behind the corner wall) around the exhaust pipe moulded thru hull housing in that back corner onto the floor. Water was also trickling down the side hull walls near the exhaust box.

    After removing the two rod holder tubes in the transom deck, that area was sopping wet from water dripping thru the clear/canvas double thread joint, and thru the corner zip, onto the ledge deck tread and running under and thru the screws threads. Net net, there was only the rubber gasket between the decktread and rod holder surround and no sealant. Over the years the gasket was showing signs of decay and certainly there was no sealant down the screwholes. Dried that area out, refixed the fittings and thought I’d nailed that leak.

    Next rain, certainly not as much water, but still an amount, plus the leaks down the hull walls next to the exhaust box. The paper towels indicated it was coming thru around the rubrail, so figured it was leaking thru the rubrail screws. That lead to removal of the rubrail curved stainless cover strip (and 50+screws) from the transom door round to the rear of the salon window to the cover strip joint.

    After removing the strip, the bolts that hold the rubrail to the hull are apparent and the nuts are accessible in the cockpit under the top lip. While there was some sealant stuck to the cover strip, that appeared to be covering most of the rubrail bolt heads attempting to stop water leaking thru, but it was obvious that no sealant had be used on the outside bolt thread. I also think that the rubrail rubber is slightly concave, particularly between the bolts holding the rail to the hull. The top edge that contact the hull wall is also critical to stop water leaking in past the rubrail, then finding its way thru an egress point.

    In any event, I figured I’d push silicon thru the cover strip screw holes and over the 50+ holes, I used the best part of a tube of silicon, which mean it was flooding the gap area behind the rubrail and was liberal with the sealant around the cover strip holes. I refixed the cover strip and resealed the top rubrail edge and also the cover strip top edge so that water could not get in from the top. After the next rain, I don’t have a drop of water, so a combination of my fixes has seemed to have worked.

    If I were to do it again, I would have backed off the rubrail bolts, releasing the edge from the hull to get the silicon in behind and then retighten, then flood the cover strip screw holes after that. I did retighten all bolts I could get to before resealing the cover strip. Certainly over time the rubrail top/bottom edges can deteriorate which would allow water to dribble in behind. Maybe allowing an unsealed 2” strip periodically on the bottom edge would allow any water that gets in to run out.

    Anyway, the ongoing project would be to keep going around the rest of the boat.... I’ll put it on the list. Hope this helps anyone that has similar leaks.

    Kevin, maybe you put this in the leak thread.

    Cheers
    John H
    Brisbane QLD Aust
    "Harbor-nating"

    2000 - 4788/Cummins 370's

    #2
    For a while I’ve had water coming in the port lasserette area next to the exhaust box. Initially I thought the exhaust box was leaking, but that was subsequently ruled out to be rainwater accumulation. Cockpit clears were also down, so the cockpit area was dry.

    Troubleshooting began by shaping a ridge of silicon about a foot forward of the transom corner (along the wood riser “wall” at rear of the battery boxes) to the side hull wall to try and isolate where the water was running in or down the hull walls. I also rammed paper towels up underneath the hull and lasserette wall joint, also along the hull chine horizontal ledge near the exhaust box, and up the gap in the back corner between the transom wall and the cockpit wall (2” gap near where the duckboard bolts come thru).

    Lots of rain discovered water coming down the interior cockpit wall (behind the corner wall) around the exhaust pipe moulded thru hull housing in that back corner onto the floor. Water was also trickling down the side hull walls near the exhaust box.

    After removing the two rod holder tubes in the transom deck, that area was sopping wet from water dripping thru the clear/canvas double thread joint, and thru the corner zip, onto the ledge deck tread and running under and thru the screws threads. Net net, there was only the rubber gasket between the decktread and rod holder surround and no sealant. Over the years the gasket was showing signs of decay and certainly there was no sealant down the screwholes. Dried that area out, refixed the fittings and thought I’d nailed that leak.

    Next rain, certainly not as much water, but still an amount, plus the leaks down the hull walls next to the exhaust box. The paper towels indicated it was coming thru around the rubrail, so figured it was leaking thru the rubrail screws. That lead to removal of the rubrail curved stainless cover strip (and 50+screws) from the transom door round to the rear of the salon window to the cover strip joint.

    After removing the strip, the bolts that hold the rubrail to the hull are apparent and the nuts are accessible in the cockpit under the top lip. While there was some sealant stuck to the cover strip, that appeared to be covering most of the rubrail bolt heads attempting to stop water leaking thru, but it was obvious that no sealant had be used on the outside bolt thread. I also think that the rubrail rubber is slightly concave, particularly between the bolts holding the rail to the hull. The top edge that contact the hull wall is also critical to stop water leaking in past the rubrail, then finding its way thru an egress point.

    In any event, I figured I’d push silicon thru the cover strip screw holes and over the 50+ holes, I used the best part of a tube of silicon, which mean it was flooding the gap area behind the rubrail and was liberal with the sealant around the cover strip holes. I refixed the cover strip and resealed the top rubrail edge and also the cover strip top edge so that water could not get in from the top. After the next rain, I don’t have a drop of water, so a combination of my fixes has seemed to have worked.

    If I were to do it again, I would have backed off the rubrail bolts, releasing the edge from the hull to get the silicon in behind and then retighten, then flood the cover strip screw holes after that. I did retighten all bolts I could get to before resealing the cover strip. Certainly over time the rubrail top/bottom edges can deteriorate which would allow water to dribble in behind. Maybe allowing an unsealed 2” strip periodically on the bottom edge would allow any water that gets in to run out.

    Anyway, the ongoing project would be to keep going around the rest of the boat.... I’ll put it on the list. Hope this helps anyone that has similar leaks.

    Kevin, maybe you put this in the leak thread.

    Cheers
    Last edited by higgins_jr; 03-23-2019, 12:53 AM. Reason: Corrections
    John H
    Brisbane QLD Aust
    "Harbor-nating"

    2000 - 4788/Cummins 370's

    Comment


    • Woodsea
      Woodsea commented
      Editing a comment
      Thanks John! Good write up! I’ve got a section of SS that a scared up a bit that I have been thinking about replacing anyway. I think I may try your screw hole caulk pumping fix. Can’t hurt right and sounds relatively easy. How long did you spend on the transom?

    • jim.sumi
      jim.sumi commented
      Editing a comment
      JOHN, thanks for starting this- I'm sure a rub rail is a rub rail and this is on my list

    #3
    John - interesting and very timely account. Thanks. I've had water getting in my starboard lazarette for quite a while. At first I thought it was from the floor of the little storage area on the side of the cockpit so I sealed up the floor of that area but no change in water ingress. I get some in the lazarette after every good rainfall or boat washing. I was planning to bring the boat into the shop to have the rubrail re-caulked all around. Do you think that will do the job or do I need to pull off the rubrail like you did?

    I did replace my rod holders about a year ago. They came with new gaskets but I don't remember using much sealant at the time. Perhaps I'll pull them out again and reseal!
    Evan
    2001 Bayliner 4788 "Fifty / Fifty II"
    League City, TX

    Comment


      #4
      Thanks for that description! I never knew how the rubrail goes together!

      Like you i’d be inclined as a first try to seal the screw heads and putting the cover back on. If that didn’t wrk then more drastic measures would be called for.

      Great write up!

      KEVIN SANDERS
      4788 LISAS WAY - SEWARD ALASKA

      Comment


        #5
        I also have rub rail leaks but more forward. I thought that an expanding foam in the screw holes. and then sealing them with sikaflex. Ureathane foam is supposed to be closed cell and shouldn't absorb water. anyone tried that fix?

        Comment


          #6
          Originally posted by egbauman View Post
          John - interesting and very timely account. Thanks. I've had water getting in my starboard lazarette for quite a while. At first I thought it was from the floor of the little storage area on the side of the cockpit so I sealed up the floor of that area but no change in water ingress. I get some in the lazarette after every good rainfall or boat washing. I was planning to bring the boat into the shop to have the rubrail re-caulked all around. Do you think that will do the job or do I need to pull off the rubrail like you did?

          I did replace my rod holders about a year ago. They came with new gaskets but I don't remember using much sealant at the time. Perhaps I'll pull them out again and reseal!
          Evan, I only pulled the s/s concave cover strip off, not the actual rubber rubrail. But I think you should attack it one step at a time, eliminating each possibility or area. I’d first remove the rod holders after the next rain and see if the ply around the screw holes etc under the tread deck glass is wet. It’s amazing how much water can leak thru screw threads, and if it’s coming down the inside wall surfaces (behind the cockpit panels) you’ll never see it till it’s on the floor. If so let it dry out and then reseal using sealant on the exposed drilled hole sides (1 1/2” thick) down the threads and under the rubber gasket. It’s tread deck, so water can leak past the raised bits. If not, replace and reseal with sealant including the thread holes and move to the next possibility.

          If if that doesn’t solve the problem, cut paper towels 2-3” wide and jam/compress in the gap up under the deck area (with one end of the towel hanging out and down a couple of inches) where the deck and the cockpit and hull edges come together. Look underneath and you’ll see maybe a 3/8” gap up there. Leave a gap of say 2” between the paper towels so you can see which paper “wick” is wet, which will help you pinpoint any egress points. You can then go to a rough area on the rubrail that needs attention. Whether you want to go to the effort of removing the s/s cover strip is up to you, but I would and it’s not hard. But put a ratchet ring spanner up onto the nuts you see under the ledge and see if you can get any movement from the bolts holding the rubrail. I got maybe 3/4 of a turn on many of them. That in itself may be part of the issue.

          When you do remove the cover strip screws, lever the bottom edge out and see if you get any water drips out from the cover strip. If so, then water is trapped behind and probably finding its way into the screw holes. If you don’t want or can’t release the main rubrail rubber, then I’d certainly jam an uncut sealant nozzle in the thread holes and start pumping. When it comes back out the hole, you can move to the next hole. That will certainly stop water getting in thru those holes and fill much of the area between the hull and rubrail, but make sure there is sealant over the rubrail bolt heads to stop any possible egress point there too. It’s not that much effort to take the s/s cover strip screws out for each say 15 ft section to expose bolts and holes for sealant. When the strip is refixed, run a thin bead along the top edge of the rubrail rubber AND the top edge of the cover strip. I did mine at the dock and can spin mine around to do the other side as required, no need to a specific haul out unless you do it in conjunction with another on the hard task.

          Let us us know how you go! Hope it helps. Cheers
          John H
          Brisbane QLD Aust
          "Harbor-nating"

          2000 - 4788/Cummins 370's

          Comment


            #7
            Originally posted by PFW View Post
            I also have rub rail leaks but more forward. I thought that an expanding foam in the screw holes. and then sealing them with sikaflex. Ureathane foam is supposed to be closed cell and shouldn't absorb water. anyone tried that fix?
            Your expanding foam idea wouldn’t be my approach when Sika will get into gaps that foam bubbles etc won’t fill. If you’re trying to seal or cap holes with Sika, the foam would be coming back out the screw holes, probably before you can release the trigger.

            Access to the rubrail bolts/nuts is certainly more difficult depending on location, but pumping and filling the cover strip holes will most probably fix the issue along with beads on the top rubber edge and where the cover strip (top edge) makes contact with the rub rail rubber. I’m in two minds whether the cover strip bottom edge needs a continuous bead to seal that edge. I found being liberal as the sealant was coming back out the hole (under the gun pressure) and ensuring the rubber bolt heads were also covered, there was enough sealant behind the cover strip and a bottom bead maybe is redundant - it also allows any water that get in behind to drain out. Certainly the bottom edge of the rub rail rubber needs a bead, but a gap here and there would allow any water behind the rubber to leak out as required.

            Good luck with it. Cheers
            John H
            Brisbane QLD Aust
            "Harbor-nating"

            2000 - 4788/Cummins 370's

            Comment


              #8
              When I fixed my rub rail leaks on my 3870 I removed the rub rail then cleaned the area and sealed the joint with 4200 as well as the screw heads.
              I do not have any more leaks from that area, the same with the drip rail above the windows.
              On my 3870 on one side of the boat only every 2nd pilot hole had a screw in it, on the other side every 3rd hole under the drip rail, and the seam joint was not sealed.
              I drilled the screw heads off on many of the bolts and knocked them in. then used screws with sealant on them.
              The water comes in under the metal portion of the rub rail from water spray.
              Pat says: DO-IT-RIGHT THE FIRST TIME!

              Bayliner 3870 "ALASKA33)
              Twin 350 GM power
              Located in Seward, AK
              Retired marine surveyor

              Comment


                #9
                Pat,
                Did drilling off the screw heads and knocking them in allow you to remove the rub rail? Did you then seal rub rail and secure with self tappers?
                2000 4788 w Cummins 370's, underhulls, swim step hull extension
                12' Rendova center console with 40HP Yamaha
                MV Kia Orana
                Currently Alameda CA

                Comment


                  #10
                  Originally posted by Woodsea View Post
                  Pat,
                  Did drilling off the screw heads and knocking them in allow you to remove the rub rail? Did you then seal rub rail and secure with self tappers?
                  I installed re-installed SS nuts and bolts, screws in those I could not access.
                  I did install a new rub rail, the type with a black poly tubing insert, you also can use rope for the insert.
                  4200 on all screws, I also sealed the seam with 4200.
                  My aluminum was nasty looking.
                  Water coms in from the bottom of the rub rail, the spray has more pressure than one would think.
                  Fisheries supply.

                  Pat
                  Pat says: DO-IT-RIGHT THE FIRST TIME!

                  Bayliner 3870 "ALASKA33)
                  Twin 350 GM power
                  Located in Seward, AK
                  Retired marine surveyor

                  Comment


                    #11
                    Hi guys. Just a follow on to this leak thread, I’m slowly working my way around the rubrail sealing the s/s insert screw holes. Today I did the 15 ft portside section under the salon side windows. I could not believe how much black silicon I pumped down the holes - 2 and 1/2 tubes. In several places as I was pumping it in, dribbles of water were dripping out underneath the rail (see pic). The major spot was in the center of the engine vent, which seems to be the lowest point of the “horizontal” rubrail (front water tank being full, lifting the stern a tad). The other dribble point (not so bad) was near the port diesel cap.

                    It it would seem that there is a significant unsealed gap/void where the top and bottom hulls come together which is then covered by the 2” rubrail rubber. Any water stuck in behind, can then find its way in thru the gaps and screw holes. I wish I had video’d the water running out, I was amazed and just kept pumping in silicon to fill the void.

                    Anyway, taking off the rubrail cover strip and filling the screw holes can certainly help to stop internal leaks, but be prepared to use up a bunch of silicon. I’m 1/3 done and I reckon I’ll go close to a dozen tubes to go all the way round the boat.

                    Cheers

                    Click image for larger version

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                    John H
                    Brisbane QLD Aust
                    "Harbor-nating"

                    2000 - 4788/Cummins 370's

                    Comment


                      #12
                      Ok I fully understand the interest in resolving any water leaks since they're the bane of any boater. The question I have is what is best to seal/bed these screws or fittings. In the past most if not all boaters warned about using silicon to do any of this type of work. The knock against silicon, that while a great sealer it's almost impossible to completely remove from any surface to which it is applied. So you get some damage to one of your rub rails and you have to remove/replace a section. Pulling it off and replacing it you have to completely remove the old gouped on sliicon. Not an easy task. Using something like sikaflex allows you to completely remove what is there and to rebed with fresh. I'm uncertain just how well new silicon adheres to the old. My experience in my earth bound bath is not good :-). Please let me know anyones actual experiences.

                      There are some very reputable boat builders/repairers that have a very firm requirement for absolutely NO silicon on boats. I'm assuming this is for good reason.

                      RB Cooper

                      Comment


                        #13
                        Originally posted by rbcooper View Post
                        Ok I fully understand the interest in resolving any water leaks since they're the bane of any boater. The question I have is what is best to seal/bed these screws or fittings. In the past most if not all boaters warned about using silicon to do any of this type of work. The knock against silicon, that while a great sealer it's almost impossible to completely remove from any surface to which it is applied. So you get some damage to one of your rub rails and you have to remove/replace a section. Pulling it off and replacing it you have to completely remove the old gouped on sliicon. Not an easy task. Using something like sikaflex allows you to completely remove what is there and to rebed with fresh. I'm uncertain just how well new silicon adheres to the old. My experience in my earth bound bath is not good :-). Please let me know anyones actual experiences.

                        There are some very reputable boat builders/repairers that have a very firm requirement for absolutely NO silicon on boats. I'm assuming this is for good reason.

                        RB Cooper
                        I use 3M 4200, it does not dry hard like 5200.
                        Pat says: DO-IT-RIGHT THE FIRST TIME!

                        Bayliner 3870 "ALASKA33)
                        Twin 350 GM power
                        Located in Seward, AK
                        Retired marine surveyor

                        Comment


                          #14
                          Pat,

                          Thanks for that, I too use 3M 4200 as a bedding compound for the exact same reason you state. However never being too old to learn new tricks I'm willing to let others experiences "enlighten" me. :-)

                          I've tried to remove silicon installed by the previous owner and it's a real bear. I'm thinking that maybe there are some new formulations that might be much better.

                          RB Cooper

                          Comment


                            #15
                            RB, while 3M product is available here, I used a locally manufactured product call Fix8 - they have a variety of silicon/adhesive products. I certainly wouldn’t be using 5200. To be honest, I’d rather get rid of the leaks and worry about cleaning/removing any silicon later, if I ever need. I would have thought freeing all the screws and thru bolts and putting a wide plastering blade up the underside of the rubrail, would free the rubber edging rather quickly. Yep I guess cleaning it off for reuse may be an issue, but replacing the thrubolts to reattach it would be a bigger hassle. Thanks for the query though..

                            Cheers

                            John H
                            Brisbane QLD Aust
                            "Harbor-nating"

                            2000 - 4788/Cummins 370's

                            Comment

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