How to reseal enclosed transom On An aluminum boat without welding?

Discussion in 'Boat Design' started by Ryan Miller, May 23, 2019.

  1. Ryan Miller
    Joined: May 2019
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    Location: Almonte, Ontario, Canada

    Ryan Miller Junior Member

    I just got an aluminum boat it is a 1996 spectrum pro avenger 16 sc with and enclosed transom but the transom wood is rotten. The transom is enclosed and welded closed. It looks like a big job i am from canada and would cost a lot to have it done professionally. I was looking into doing it myself. I do not own a welder so was looking for away to reseal the transom without welding it back. I will grind out the top of the transom and take out the old rotten wood then put new sealed wood in. Then can i just take sheet metal bent at 90 degrees and rivet it back on with marine sealant underneath. Or would i have to weld the old weld spots back it is only welded on the corners.
     

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  2. Sean Duval
    Joined: Mar 2019
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    Location: yuma az

    Sean Duval Junior Member

    There are many here more knowledgeable than me....take what they say over what I say.

    Transom repairs are not horribly difficult....but the transom wood usually goes ALL the way across the transom of the boat....from one side to the other as one solid piece. So the welds that I see in the picture in the corner of the cutout are not a big problem....because that whole top cover would be coming off as one piece from port to starboard. And the wood would need to be removed ideally as one piece as well so it can be used as a template for your new transom.
    Please if you would provide pictures of both corners of the transom where it does a 90 and ties into the rest of tbe hull... and a whole transom view from inside and outside. From the looks of it they have welded the top piece in...and the only way to remove would be cutting those welds...

    On my starcraft the entire boat is riveted construction....and I had to drill all the rivets out....remove the screws on the corner caps....pull the motor well are back a bit....and remove the riveted on Hull ID Number to pull out the wood. Fortunately as rotten as it was I was able to lay it on a piece of marine ply and outline it so that very little fitting was needed. I couldn't get 1.5" marine ply in Yuma az, so I used 3 layers of 0.5" marine ply and epoxies them together and clamped via screws that I later removed and filled the holes with epoxy.
    Not sure if I can find pictures of the process...but...I believe you are stuck removing the entire top cap of the transom to pull the wood out for replacement.

    Additionally...
    If they welded in the top after they put in the wood how did they seal the wood and not scorch it?
    Maybe they installed the motor well last and place the wood from inside once the welds done.

    Yes rivets can be nearly as strong as welds...but I mean real ones you buck not pop rivets.

    Definitely need more pictures.
     
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  3. Ryan Miller
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    Ryan Miller Junior Member

    I think I might be able to cut those welds and just bend the aluminum take out the transom then bend the aluminum back down and self tap the top aluminum back to the back of the transom
     

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  4. Sean Duval
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    Location: yuma az

    Sean Duval Junior Member

    You may be right.
    As I understand it the wood is the strength....the aluminum sheathing protects and enhances the strength...the top cap simply keeps water out and makes it look good. I would attempt to get it off as one piece of aluminum if possible.

    Now for the disclaimer...

    "For God's sake, please let someone more knowledgeable chime in before you follow my suggestions....sometimes I'm an idiot, just ask my wife LOL.
     
  5. gonzo
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    gonzo Senior Member

    You can replace the top with an aluminum channel of the right dimension. If the sides of the channel are about 1.5 " or so, you can use 5200 or similar and screw into the wood every 6".
     
  6. Ad Hoc
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    Ad Hoc Naval Architect

    I am not familiar with this type of boat at all.
    However, why oh why would you have aluminium and wood together.....of course there will be corrosion.

    And you should never screw anything directly through the ally into the wood...another path for corrosion to occur.

    It is called poultice corrosion.
     
  7. Sean Duval
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    Sean Duval Junior Member

    Yes but remarkably in freshwater boats the wood always goes 1st.
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    If the metal is well painted, poultice corrosion less likely. But in the right conditions, poultice corrosion can make one hell of a mess.
     
  9. Ryan Miller
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    Ryan Miller Junior Member

    It is only a 16 foot aluminum fishing boat it came from factory like that but the transom wood was coated and sealed and the aluminum boat is painted with marine paint and coated so the wood does not actually touch the aluminum
     

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  10. Ad Hoc
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    Ad Hoc Naval Architect

    In that case, it is "usually" ok.
    But as soon as you use fastenings to attach the 2 parts together, is where it goes wrong, as the seal is broken.
     
  11. Barry
    Joined: Mar 2002
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    Barry Senior Member

    I would go with the idea to get someone to reweld the joint back together
    When you remove the transom cap, by using a cut off blade or even a jig saw would work, hacksaw even, you may find immediately below the weld in the corner, will be an almost 90 degree
    corner made of thin sheet aluminum. A perfect place for a crack to start and propagate down into the transom. I suspect that the weld in the corner may have provided additional
    strength to keep this from happening.
    As it appears that you have to remove the cap, send some pictures of what is beneath.
    You should be able to use the same cap that you take off.
    there looks to be maybe an hour or so of welding, so maybe a hundred bucks. Cheap insurance to inhibit a crack starting in the corner
     
  12. gonzo
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    gonzo Senior Member

    There are hundreds of thousands of small aluminum boats with a channel cap on the transom. It is a well proven design. Screws or pop-rivets is a common way of installing the cap.
     
  13. Barry
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    Barry Senior Member

    Certainly true but not often with an encapsulated wooden transom.
    This is a poor design and is the reason for the rot in the wood. (are they still around)
    There about a dozen bolt penetrations and perhaps 2 well penetrations that don't look to be sealed properly that permitted the water to get into the wood that would have caused the rot
    The sharp corner is a concern for crack propagation. If the OP is serious of a proper long term repair

    The OP should not use treated plywood as there is a good chance that the chemical may increase the corrosion of the aluminum

    Are there any current manufacturers of aluminum boats that attempt to encase a wood transom?
     
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  14. gonzo
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    gonzo Senior Member

    Yes, it is the standard reinforcement in aluminum boats. The OP's boat is 23 years old. If the repair is done with painted instead of bare plywood, it can be expected to last at least 35 years. I don't understand all the naysayers calling that bad.
     

  15. Sean Duval
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    Sean Duval Junior Member

    Agreed painted works, penetrating epoxy works better I think, but only if sealed 100% else paint wins. Worst case is 99.99 sealed gets wet and never dries as it would rot quickly that way. In short paint may be a safer option without meticulous attention to detail.

    Where I am in the desert Southwest USA I have seen unsealed transoms survive for a decade or 2
     
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