1980 four winns - wet transom

Discussion in 'Fiberglass and Composite Boat Building' started by atengnr, Nov 19, 2019.

  1. atengnr
    Joined: Jun 2006
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    atengnr Junior Member

    Thanks. If you all approve, I think Im going to cut out the rot seen, from the hull surface, laterally out to the margin of the bilge, and up above the lower engine mount holes. I would plan to use epoxy filler with cabosil (and perhaps 1/4" Chopped strand)??) to bed this into the outer skin and the surrounding existing transom core. Lastly if it would help, I would glass this in with overlap into bilge and out onto existing inner glass on transom. Sound OK?
     
  2. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    You don't want the chopped strand in there.

    Otherwise, good.

    csm or ground fibers tend to make bulky areas as a filler and you would have trouble getting the new ply core to seat and it would be humpy
     
  3. Blueknarr
    Joined: Aug 2017
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    Blueknarr Senior Member

    I second the Fallguy.

    With one added thought. Test fit the new plywood. Mark where known thrubolts or fasteners will go. Oversized drill out the fastener locations and fill with thickened epoxy. If the fastener leaks, water won't immediately saturate and start rotting the core.
     
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  4. fallguy
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    fallguy Senior Member

    Yeah. All through holes in ply get overbores and you redrill smaller for the fastening that is then bedded in say 4200..

    overbore 1/4" generlly
     
  5. atengnr
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    atengnr Junior Member

    Thanks all!
     
  6. atengnr
    Joined: Jun 2006
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    atengnr Junior Member

    Quick question. Transom is still drying out. The areas that I have exposed are pretty dry even at depth. I notice though that with the motor tilted, applying heavy pressure to the cav plate produces a slight amount of flex (it seems anyway), perhaps 1/8" or less, but just doesn't feel rock solid. Is it OK if there is this amount of flex or is this a sign that there is more extensive rot than I have uncovered??
     
  7. fallguy
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    fallguy Senior Member

    The transom ought not flex that much.

    As for more extensive rot; it is impossible to say and requires physical inspection. But you are checking against an already compromised transom.

    Have you tried tap testing?

    You would take a small plastic mallet or back of a screwdriver and hit the boat from the outside. Hit it in a known rotten spot and a known good spot and see if you can discern a different audible tone. If you can discern that tone then you tap the entire transom, listening for that rotten area noise.

    You can also see if you can physically push and see or feel the transom skin move on rotten areas (delamination), but that is not highly likely in your situation.
     
  8. atengnr
    Joined: Jun 2006
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    atengnr Junior Member

    It might be only 1/16th. Yes there is rot but seems a smaller area than i would expect to allow flex. Above the floor i believe i have the extent of rot covered. Below the floor i know from examining the screw holes for speedo and depthfinder on starboard - which was solid, and swim ladder on port side which is also rock solid.
     

  9. atengnr
    Joined: Jun 2006
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    atengnr Junior Member

    It was just loose upper engine mount bolts causing the movement. I sounded the transom the best i could and the thuddy areas seemed to be where i have uncovered
     
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