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  • Stern/Scupper Repair Advice

    Hi all,

    I'm looking for advice on the best way to tackle a repair to the stern on a 1973 20'. I have a few issues going on, but here's the background:

    The boat was completely rebuilt stringers up about 10 years ago. The transom has 1/4" of glass over 2x 3/4 marine ply. The deck was then filleted/tabbed into that, and afterward, scuppers cut through at the deck line. This is where I'm having the issue. both scuppers developed a crack where the deck meets the transom (see pic) -- in addition, the glass inside the scupper is delamination around the entire opening. Ignore the fungus thats a bonus.

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    I ground down the crack and it seems to be what I suspected, not a compromised transom, but the deck must be flexing and pulled away from the stern where the tab was removed to cut the scupper hole. The deck does seem a bit wet at that seam. the delimitation around the perimeter seems to be from where the glass inside the scupper hole meets the transom glass, and there was no overlap between the two (see below pic). Ignore the cap, there are also some issues with some voids breaking through on that that is repair #2 after I finish the scuppers.

    So my plan/questions

    1) Plan: repair with Epoxy & biaxial cloth, scarfing out into the deck and interior of the scupper at deck level. The West 4" biaxial tape would be the easiest for me to source.
    2) Questions: How do I dry out what portion of the edge of the deck that is wet, or does it matter if I don't? How much do I need to scarf into the deck for a good bond? How do I best deal with the rest of the delimitation around the perimeter?

    Thanks all for any assistance


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  • #2
    I'll give it another shot 😅
    I'm going to scarf in the deck to the transom and have it mostly ground down. Can anyone with some epoxy experience assist with these?

    1) Will the glass bond to the remaining fairing putty, or does that all need to be removed?
    2) The original scupper only had 1 layer of glass on the interior, so I'm going to add 1 or 2 more to the top, any advice how to get the glass to stay firmly attached while it cures? The bottom I'll wrap the initial large layer around the corners then layer up the scarf area from there.

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    Last edited by klaedi; 06-02-2021, 02:01 PM.

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    • #3
      1 - As long as the remaining fairing putty is attached well the new epoxy should stick to it fine. Epoxy sticks well to almost everything, it is polyester resin that doesn't stick as well to epoxy.

      2 - I would expect a layer or two of glass to stick to the top of the scupper cut-out no problem. Are you planning to bring the cloth out of the scupper cut-out and onto the vertical of the transom? I'd radius that edge and bring the glass a few inches onto the transom. That should help prevent the cracking that you show in your first pics. Will need some new paint to make it look good though
      Toronto, Canada
      76 Mako 23
      https://forum.classicmako.com/forum/...t-s-23-rebuild

      Comment


      • #4
        Originally posted by jamie View Post
        1 - As long as the remaining fairing putty is attached well the new epoxy should stick to it fine. Epoxy sticks well to almost everything, it is polyester resin that doesn't stick as well to epoxy.

        2 - I would expect a layer or two of glass to stick to the top of the scupper cut-out no problem. Are you planning to bring the cloth out of the scupper cut-out and onto the vertical of the transom? I'd radius that edge and bring the glass a few inches onto the transom. That should help prevent the cracking that you show in your first pics. Will need some new paint to make it look good though
        Thanks a lot for the feedback -- yes I was planning on doing exactly that for the interior (wrapping 1-2in onto the transom), and have the paint. $400 worth of paint supplies for a 6 inch square I haven't decided on the exterior only because that would involve more paint work for a second color and that area doesn't seem to be under as much stress.

        One worry I have is someone on another site thought the voids on the transom cap could be due to swelling -- I think from what I can see after opening it up its more likely that it was voids in the only one layer of non-structural glass that was used, like was done with the scuppers, but its a nagging thought. I'm not sure where the wetness for swelling would have come from. I'm more concerned that there may some remaining moisture in what had been the exposed transom in the scupper area from some recent wet weather (my tarp leaks along with the tape I had covered the exposed area with), though I did hit the area with a heat gun several times before I sealed it back up with a small plug and the first coat last night. The surface was definitely dry (see pics below, last is from this am -- it's raining you can see why I wanted to seal it up).

        Does anyone know if Alexseal primer can sit for a few months before being topcoated? I'd prefer to get the glass work done and primed and in the water and not spend more time fiddling with the finish coat until later this season if I can get away with it.

        As dry as I could get it with a heat gun:
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        First plug in to fill the divot, next will be full 2 more 4" strips to scarf it in:
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        Comment


        • #5
          Klaedi it looks like you are on the right track for this repair.

          About the boat.... you mentioned this boat being a Mako 20? I ask because I remember seeing a similar scupper set up on another Mako 20 rebuild.

          Here's the rebuild thread I am referencing.....go to pages 21/22 to see the details on the scupper work.

          https://forum.classicmako.com/forum/...15-16-projects

          Good luck with the repair...keep us posted.

          Eric
          A wise man once said, "Son... if it has tits, tires or a transom... sooner or later it's gonna give you problems." -the old man

          1972 Classic Mako 19
          https://forum.classicmako.com/forum/...t-squot-ole-19

          Comment


          • #6
            Originally posted by PoleLock View Post
            About the boat.... you mentioned this boat being a Mako 20? I ask because I remember seeing a similar scupper set up on another Mako 20 rebuild.

            Here's the rebuild thread I am referencing.....go to pages 21/22 to see the details on the scupper work.

            https://forum.classicmako.com/forum/...15-16-projects

            Good luck with the repair...keep us posted.

            Eric
            Thanks Eric -- yep thats her, bought off Chris a few years ago, I went through his full build thread before purchase he put a lot of work into it. Its been great to me so far outside a few issues that I expected would crop up. I'm chasing a few minor things besides this scupper area:

            Oil is slowly leaking into cowling, I can't trace the source hose or fitting yet.
            Fuel vent line(s) seems clogged or crimped -- I have to fill the tank very slowly. Haven't looked into where to start with this.
            Power drop from helm batteries to starter makes cold starts difficult (may need new cables or at least crimps, but I need to check all connections first).
            Need to raise the engine a pin to get WOT RPMS up -- going to do that this week once I settle on what I want to re-seal the underwater bolts with (leaning towards marine caulking -- boat life or equiv).
            Debating replacing the cable steering w SeaStar, but want to fiddle with the trim tab first.

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            • #7
              Documenting this all for the hell of it:

              I decided to round out the exterior and wrap glass there also and I'm glad I did -- the original exterior skin was delaminating a bit from the core at the edges, though that had been layered over with some 1708 before bonding to the skin so no (or at least limited) water to wood. I filled the gap with as much resin as I could then put down the first layer of biaxial glass. I can see anything beyond vertical is going to be a challenge I had to keep working the glass until the resin kicked off to get it to remain in place, and I only went part way up the sides of the opening.

              Pics below:
              Black wood near the flapper screwhole-- problem???
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              1" overlap to exterior transom -- slight delamination where old skin meets new transom:
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              1st exterior wrap done:
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              interior side:
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              Last edited by klaedi; 06-09-2021, 05:27 PM.

              Comment


              • #8
                By the way -- this thing was the best $35 spent to grind into these tight areas with minimal dust, just use a vacuum. Doesn't seem available anymore so prob junk but it does the job:

                https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

                Comment


                • #9
                  Advice needed here --

                  1) I ended up with a void on the radius, am I better off grinding that out and patching (don't think that is considered structural area), or am I ok drilling a small hole and injecting epoxy?

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                  2) The vertical walls were tough, I'm not sure how I'm going to manage a radius for the top, any advice on that also? thicken the epoxy, or cut the cloth oversize and tape it in place? Put some visqueen over it and pull it tight/tape?

                  3) I glassed over the small screw holes for the flapper cover, but didnt fill them first, should I do anything about that? Drill/fill, leave it?

                  4) Should 1 layer if biaxial be enough for the vertical and top wrap? 1 feels pretty bullet proof compared to what was there prior but I'm going for 2 on the deck level to be sure just hope it still drains well.
                  Last edited by klaedi; 06-09-2021, 05:26 PM.

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                  • #10
                    To keep the glass shape inside the scupper you can try blowing up a ballon inside to press the glass in place. Never done it but saw it here once.
                    1978 Mako 25 - Blind Hog
                    1985 Mako 20c - sold
                    Fort Walton Beach, FL
                    https://forum.classicmako.com/forum/...og-bottom-time

                    Comment


                    • #11
                      Originally posted by Sailor View Post
                      To keep the glass shape inside the scupper you can try blowing up a ballon inside to press the glass in place. Never done it but saw it here once.
                      That's on my short list but also want to get it wrapped around the upper radius without sagging. Maybe I'll do glass/visqueen/balloon and separate the top/side pieces into 3 separate sections. I don't want to have to do this again and need it buttoned up tight.

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