thompson 240 transom rebuild

newtoboat101

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Jul 9, 2015
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412
1988 thompson 240 fisherman fiberglass boat rebuild transom (see pics), my question is now that i have removed everything from the transom (trim tabs ,kicker motor bracket speedo tube ,and some other hardware) do i (1) replace the transom wood and fiberglass on the inside first then fill in the holes on outside ,or (2) tape the back side and fix holes then replace transom inside or (3) put a layer of 1708 on inside of transom then apply wood and fiberglass over it then fill holes from outside ,i think all the holes in transom has me a little concerned and intimidated ,any help or suggestion appreciated .some of the holes will be reused ,kicker motor bracket will be moved slightly thank you
 

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Scott Danforth

Grumpy Vintage Moderator still playing with boats
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I recommend working on the inside. Being 1988, and a Thompson (during the 80's transition period), I am pretty sure that once you get to the stringers, you will also be replacing all the stringers,
 

MikeSchinlaub

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Jan 14, 2025
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Grind all of that leftover later of wood off. If you want to do any patch work, I would do it from the inside. It will be stronger and avoid bodywork and paint.
 

Chris1956

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Mar 25, 2004
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Replace transom and other rotten parts from the inside, if you can. This preserves the original fiberglass of the transom, which is obviously structural. A lot of times you will need to remove the cap from the hull to have ready access to the inside of the transom and the stringers, deck, etc..

On my speedboat (which is painted), I replaced the transom from the outside, to avoid pulling the cap. After wrapping the new transom with fiberglass, a coat of paint was all that was needed.

When installing a new transom, you will need some way to clamp or otherwise fasten the new transom to the stringers, deck and whatever fiberglass remains, until the new glass and resin set. On my speedboat, I glassed in blocks (think nailers when framing a house) to screw the new transom to and clamped whatever I could until the resin set. Use only stainless steel hardware for any fasteners that will remain installed.
 

tpenfield

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There are lots of restoration threads that you can/should review to see how it is done. In general, don't worry about the existing holes as you will be replacing the core of the transom from the inside. The outdrive 'keyhole' will be of particular importance as that is your engine alignment. Also careful attention to the height and spacing of the engine mount stringers . . . else you will have a 'mell of a hess' when you go to re-install the engine.
 

newtoboat101

Chief Petty Officer
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Jul 9, 2015
Messages
412
There are lots of restoration threads that you can/should review to see how it is done. In general, don't worry about the existing holes as you will be replacing the core of the transom from the inside. The outdrive 'keyhole' will be of particular importance as that is your engine alignment. Also careful attention to the height and spacing of the engine mount stringers . . . else you will have a 'mell of a hess' when you go to re-install the engine.
spent about a year watching videos before i took the bull by the horns ,frisco boater ,fish bumptv ,boat works ,michael romer ,and many more ,now i got to a point in my project where i was trying to figure best way to replace transom wood and take care of my swiss cheese fiberglass transom thanx for your advice greatly appreciated to all who comment put my project on a 2 year plan transom and stringer replacement
 
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