Transom: next steps

[TMO8413]

Picked up this Duranautic Coastal 13 this past winter. I removed the transom wood as it was rotted and learned the prior owner put some type of metal plate on the back and front of the transom (see pictures). When I pulled it off it revealed a very pitted and corroded transom on both sides. In fact, it’s pretty brittle and I could probably pierce right through it. Is the transom junk? I was thinking I could sand and paint both sides of the metal that’s left, sand and paint the metal plates, and rebolt but I’m not sure that’s help. Any thoughts on next steps would be appreciated.

 

[Stand Up]

That's ugly. I would think that you need to replace the transom. It looks like a lot of hassle to repair that corrosion. However, if you think it can be repaired, I'd like to know what your plan of attack will be.

 

[LDUBS]

There was a relatively recent thread where a guy epoxied a transom skin to the inside of his old corroded transom. It came out pretty good. If I did things right, the following link should take you there:

https://www.tinboats.net/threads/tr...tarcraft-superfisherman-176.51160/post-508390

 

[TMO8413]

Thanks for directing me to that, I like his process. I ended up taking a SS wire brush and knocked the corrosion and rust off the front and back of the transom skid. It’s pitted all the way through in some spots but just in the center. I also use a grinding disc on the steel plate plates that were sandwiching the transom skin together.

I suppose next steps are to prime and paint with an anti corrosive/rust prohibitor all surfaces and then bolt the steel plates back on with SS hardware.

I’ve got a nice piece of hard solid pvc/plastic that I am going to cut and use for the transom board. The transom brace is solid so I don’t think this will compromise its integrity. Only going to put a 9.9/15HP on it anyway. Thoughts on my decision?

 

[airshot]

I would make new plates that are larger to spread out the force that motor will put on that transom. Eve using a couple pcs of 3/4" plywood , one on each side that are larger than what you removed...that corroded part has lost much of its strength, so I would sandwich it between two larger pieces to get strength back.My .02 cents anyway..

 

[LDUBS]

I know nothing about PVC boards other than they exist. I assume you will be layering it for thickness. How does it compare in rigidity to plywood? Sure would be great for avoiding rot.

I wonder if it would be a good idea to batter both sides between the plates (not the PVC) with something like 3M 5200? It would be essentially permanent which might be good or bad, I suppose. Maybe folks can weigh in.

 

[lckstckn2smknbrls2]

Install an all-aluminum transom. It can carry the weight of the motor and forces applied on the transom. Then you can epoxy a new aluminum skin to the transom.

 

[TMO8413]

I was also thinking that as well, LSHOT. Maybe fabricate new aluminum or steel plates that are wider to bit into the stronger part of the transom. But would plywood be stronger? I also know nothing of the strength of this pvc/plastic board but at the very least. I know it won’t rot. I’ll be stacking it.

I saw a video of someone who used a 12x12 sheet of a T6 aluminum plate at 1/4 thickness. Was thinking I could buy two of those and slap them on…maybe I only need one for the back? Is 1/4 too thick? They also have 1/16.


Thanks all who chimed in.

 

[airshot]

An aluminum backer would be stronger as long as it is bigger than your corroded area ! Might be costly....plywood would give the same or better strength at probably less cost. Aluminum would last longer, but plywood would outlive your lifetime if sealed. The biggest advantage to plywood is it gives your clamp on motor something to bite on. Clamping to aluminum can be sketchy, most all aluminum transoms have the motors bolted onto them. Smaller clamped on motors hold better on wood.

 

[TMO8413]

An aluminum backer would be stronger as long as it is bigger than your corroded area ! Might be costly....plywood would give the same or better strength at probably less cost. Aluminum would last longer, but plywood would outlive your lifetime if sealed. The biggest advantage to plywood is it gives your clamp on motor something to bite on. Clamping to aluminum can be sketchy, most all aluminum transoms have the motors bolted onto them. Smaller clamped on motors hold better on wood.

I’m just talking about sandwiching the front and back of the transom skin in 1/4 aluminum to reinforce and give more strength to the missing and corroded transom skin. I’ll likely 3M 5200 on both sides, bolt it down with stainless, and vice grip for a week. That way, when I go to put in my plywood or plastic/pvc, I’ll have a solid backing to support a motor. I hope I am making sense.

I was going to go T6 aluminum but that sounds like overkill. Anyone know of 5052 aluminum would be just as strong?

Thanks again all. I’ll include pictures once I spend a small fortune….

 

[thill]

I would skin the area on the outside with aluminum. Bed it in epoxy, is what I would do.

For the core, I recommend against using Azek or other PVC boards, unless you have the tiniest little motor on the back. They are soft and rubbery, and will flex and take a "set" if weight is applied over time. Your transom will end up sagged out unless the brace helps enough to hold it straight.

Use a double-layer of plywood, or you can use a stack of 2x8 in Southern Yellow Pine (SYP) glued and sealed together with a skin on the inside, if you simply don't want to deal with plywood.

There are many ways to skin a cat, but how you go about it will determine what kind of cat it will be.