Support Transom 1990 SeaNymph TX150 Rotten core

[Dizz]

Hi guys,been member here for years,but not been around long time.
Hope someone has solution better than my idea.
On the transom,the wood core sandwiched my perhaps 1/16" thick aluminum dry rotted ages ago,you can tell because the 15hp Evinrude mount screws never get tight enough.
In 07 I reinforced it with a inside layer full contact 3/8" plywwod.it got me by.
now I`m seeing way to much flex in the transom under power,and fear the metal will break.
I`m thinking rather than rebuilding total transom,what if I replace the inside plywood with .25" thick aluminum plate fell contact?
Looks like I`d barely have room for new 3/8" plywood and still fit the motor clamp on it.I`d go again full length stainless bolts,and rubber seals,or RTV that`s worked all these years.
Will this work?
Appreciate any thoughts on this.

 

[GA_Boater]

Sandwiching rotted mulch is not really a fix. If it works! Since it has nothing solid to work against, you will be tightening the clamps more and more, even with all the build up cover ups.

Why not replace the transom wood the correct way instead of sticking bandaids on it?

 

[Dizz]

How would this be done,by cutting the whole top plate,dig out old,slide new in,then TIG,or whatever aluminum weld cover back on?

 

[GA_Boater]

Pictures help.

But yes, trim off what's needed on top of the transom to get the wood out. Them find some aluminum channel to cap the transom. No need to weld anything. Small screws or boat nails will hold the new trim piece in place.

 

[Dizz]

Looking at this transom in the daylight,trying to replace the wood,that goes all the way to side ends,east to west of the transom,would be near impossible.The way the top strip,has wings welded to top side wings,would block getting all the wood out.Much of this wood would be in good shape,couldn`t dig it out in a month of Sundy`s.It`s only weal where it needs to be strong,where the clams are.it has bolts holding the motor on,thru to outside to under water,in addition to the usual clamps,water seepage over the years.Proper repair much reconstruction,much welding$$$$$$.
I see no answer feasible on this old boat except a bandaid!

 

[airshot]

Pictures might help the members give you some additional ideas. Band aid fixes never work for long and frequently cause serious damage or injury to people. I have replaced wood in alum boat transoms in the past and it is not that bad of a job. Typically the alum pieces are riveted together so drilling out rivets and taking it apart then reassembling with screws or new rivets is the norm. In case of welded areas the weld can be cut thru then bolted back together after new wood is replaced. On the few I have done, a Saturday is all I have needed to complete the job. Have you ever saw a transom blow out on a boat traveling across the water at any speed? It is not a pretty picture, plus you loose all your gear and if the fuel tank sinks then you will have very heavy EPA fines like you will not believe. And if you have insurance on the outfit it will not be covered if you make a band aid repair. My old neighbor can attest to that.

 

[Dizz]

I`ve come up with a idea.This boat has wood floor&carpet,a mini bass boat.It has the 15HP Evinrude that came with it,so not a speed boat,17mph tops. ​If I take the seats&floor out,I can get to the inside of the alum sandwich.
I don`t see any rivets to make access easy,may see more as I get deeper in it,but looks to all be welded together.
looks like I`ll have to cut this inside piece along the edges.Dosen`t look like I`ll be able to replace the outside 1' of wood on each end,but still a good fix I think.
I bought a 12' 2"x12" treated at Lowes.no sell shorter planks.
I`ll replace as much length as possible,and NOT install back the inside sheet of aluminum,toprevent sealed up wood to leach water into it,and repeat this in the future.
The original wood looks to be close to 2' thick +-.
I can always add a layer of 1/2" treated plywood if needed.
the rear aluminum on my boat is caved in over 1" from the motor mount&pressure,I`ll straighten this out tapping a wood plade&mild hitting.
Will post back as I`m able to work on it weekends.
I think this will be much better&permanent than my other ideas,what do you think?
Appreciate the feed back on this!

 

[krakatoa]

Pictures said more than a thousand words.

Anyway its looks like you already decided to put a bandaid to your transom, its not save, its not a good idea.

 

[Dizz]

This is not a bandaid?
I just dug the completely rotten wood,it was two layers of 3/4" plywood when built 26 years ago.
I`m able to replace all the wood,but it will have a joint for 12" on left corner.
This boat has a ledge with carpet that runs down both sides,5" down from top sides.These aluminum support ledges would require cutting all the rivets,to remove,to expose entire rear inside transom,bottom and sides..I`ve had bad luck replacing factory boat rivets in the past,and this boat has no leaks.
All the wood will be replaced,from two layers of plywood,to solid new treated 2x12.
I can rebuild an engine,but not savy on the forums posting pictures.My 1st boat was a 62 model Montgomery Wards 14' flat bottom,with a Ted Williams 7.5 made by nobody I could find out who.I used it in 1970.
I took a few pics,and could send pics to a cellphone.
Many Thanks guys,you are tough!

 

[airshot]

Do NOT use treated plywood on or near aluminum...it will cause a chemical reaction and cause the aluminum to deteriorate in very short order. Many posts on here have gone to great lengths to warn people of this. Use NON treated lumber,,,never treated in an aluminum boat!

 

[jbcurt00]

Dizz
Post some pix of your boat and transom.

Never seen an aluminum boat that couldnt have the transom plywood replaced in 1 long piece, but that may require more work then you'd loke to hear.. A splice or 2nd 12in piece isnt a good idea either.

Hundreds of guys here have replaced thousands amd thousands of factory rivets w no long term problems.

 

[Dizz]

Sure appreciate the tip on treated lumber.In 02 I replaced all the floor with treated,no damage,but this was likely before the copper used now.​I`ll use regular spruce,with oil base floor grey paint.
Againsorry for no pics,but if you could see the wings above the transom,like the old 59 Chevy Impala,that are welded on,I`m not going to rebuild the rear end,as this is going to be 10 times better than it has been since 02,and the transom core was junk then.
Only use it at most twice a year.i`m also going to run 20" supports of 2x12 up the inside walls to connect to transom for added support,it will be like a tank,but not perfect.
Thank`s To All!!
In 4 years I`l be 65,retire,and will get a all aluminum boat like a grizzly,no more carpet&plywood for me!

 

[Dizz]

Found out today,not just the wood has decayed.
the entire aluminum rear transom has many tiny corrosion holes from 26 years,with rotten wet marine plywood from the factory,all the pits are from inside out.
I suppose a fabrication shop could cut the rear section out,weld new rear cap back on.
I`m guessing $500,and much work to get it ready.