Transom in Aluminum Boat Question

[Bass Runner]

Ready to replace the transom in my Texas Maid, but i have a question, the original transom i took out was just treated and not glassed, I am putting douglas fir plywood back in it, what can i treat it with? The wood part of the transom is 1 1/4" and can't really do any combos with glass and mat and get it to fit. I was think of tompsons water seal will that work or should i paint it with a oil base marine paint? The original floor was also just treated 7/16" plywood it wasn't marine plywood and in pretty good condition except where the boat was full of leaves and it was rotted there, all the floor in the nose was still in good shape so i am putting it back in, i am replacing the floor in the back with douglas fir also. Here is a look at the sub floor on my web page. Texas Maid

 

[Bass Runner]

Re: Transom in Aluminum Boat Question

Nobody has ever just treated a transom instead of glassing it?? I need some pointers from the experinced, as to what to treat the plywood with that will protect the wood in the transom. Thanks

 

[Ken G]

Re: Transom in Aluminum Boat Question

Anything you do to seal your new transom will probably be better than it came from the factory. My first project boat was an old Sea Nymph. When I removed the transom the plywood was unrecognizable. I replaced it with 2 layers of 3/4" Mahogany marine plywood laminated together with epoxy and covered overall with 2 coats of epoxy. On this boat the only part of the transom that is uncovered is beneath the splashwell in the bilge area. The bottom edge is above the floor so the wood in the transom never really gets wet. I sealed all bolt holes with 3M 4200 sealant. This transom rebuild was probably overkill. <br /><br />For the floor I used 15/32" BC exterior plywood with 3 coats of Spar Urethane varnish. Most of the floor is covered with exterior carpet and seems to be holding up well. Part of the front deck was 5/8" BC plywood with the same treatment but I never installed the carpet. After one season the surface seemed to be 'checking' along the grain so I lightly sanded it and painted it with 2 coats of porch and deck paint. The paint and wood is holding up great and that deck gets wet alot from throwing a cast net and having a wet anchor line coiled on it.<br /><br />My current project is a 21' Starcraft. What's left of the old transom is still in the boat but it appears to be exterior plywood with a coat of paint on it. Part of the inside of the transom is exposed in the splashwell with no aluminum skin covering it. When I replace it I will probably still use the mahogany marine plywood because of its strength and the ease of using it. The panels are absolutely flat which is hard to find in regular plywood. I'm undecided about laminating the panels together with epoxy or using Gorilla Glue. When reinstalling I will probably fabricate an aluminum skin to cover the transom inside the splashwell. Since the transom will no longer have any areas exposed to the elements I will probably cover it with a couple of coats of the porch and deck paint. If my rebuild lasts half as long as the original I'll be in good shape since the boat is 34 years old.<br /><br />The original floor in the Starcraft was pretty bad but some panels still had the ACX plywood stencil on the bottom side. The plywood appeared to be unsealed. I don't know if the floor originally had a vinyl covering or carpet. The new floor will be BC plywood sealed with paint and then covered on top with either grainy vinyl or a roll on non-slip coating like Durabak.

 

[quantumleap]

Re: Transom in Aluminum Boat Question

Check out the rotdoctor http://www.rotdoctor.com/ and the tests they did on plywood with their CPES. It's about a hundred times better than Thomsons Waterseal.

 

[Bass Runner]

Re: Transom in Aluminum Boat Question

Thanks for the info, another question along the same lines is I have two motor mount bolt holes and other various small screw holes in the metal part of the transom, I found a oil base aluminum silicone that gas is not supposed to hurt and it is paintable, would that be ok to seal the holes with when I put the transom back in? and install the new motor mount bolts (different from the ones already in it (naturaly)

 

[Ken G]

Re: Transom in Aluminum Boat Question

Every silicone based product I've seen say somewhere they are not for below the waterline use, but don't tell that to the 50 aquariums I used to own. You'd be better off with a polyurethane based product from 3M or similar. 3M 5200 is a permanent sealant, 4200 is semi-permanent. I used 4200 on my bolts figuring I will need to remove them some day.<br /><br />For the old holes I'd use Marine-tex or at least 3M 5200. You might even consider using the 5200 with a stainless steel pan head screw in the old screw holes.

 

[quantumleap]

Re: Transom in Aluminum Boat Question

I've had excellent luck with the 3M 4200.<br /><br /> You make a good point Ken. I knew a guy in college who's dad owned a glass shop. Well, he made a fish aquarium and put it together in his house with nothing but 100% silicone holding it together at the seams. No framework at all. It held 150 gallons of water and sat on an old oak table in the kitchen four three years and never leaked a drop. I always expected it to rip apart from the water weight but it never did.

 

[Bass Runner]

Re: Transom in Aluminum Boat Question

Originally posted by Ken G:<br /> Every silicone based product I've seen say somewhere they are not for below the waterline use, but don't tell that to the 50 aquariums I used to own. You'd be better off with a polyurethane based product from 3M or similar. 3M 5200 is a permanent sealant, 4200 is semi-permanent. I used 4200 on my bolts figuring I will need to remove them some day.<br /><br />For the old holes I'd use Marine-tex or at least 3M 5200. You might even consider using the 5200 with a stainless steel pan head screw in the old screw holes.

The silicone I have is made by GE, it is also polyurethane based and says you can use it after cured in water, for use with glass, aluminum, steel, wood, and plastic, so i guess from what you say it will be ok for sealing the holes. Right?