Rotten Transom

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rprice1012

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Bowling Green, KY
The wood underneath the metal brace of my transom is rotten and needs to be replaced. I'm kind of in the dark about these kinds of things, as this is my first boat. It's a 1971 14' Appleby and has a 1964 5.5hp Johnson Sea Horse outboard motor. What steps do I take to keep my motor in the boat and what type of wood do I use? What is "marine grade" wood anyways?

Thanks friends!
 
Don't bother with marine grade ply.

I used layers of oak plywood glued together to get the appropriate thickness and then coat that with a few coats of spar urethane to protect it.
 
Exterior grade plywood is where its at. Same glue that is used in marine grade, but the difference is it's not guaranteed to be free of voids--which is not worth spending 2 or 3 times the cost of exterior grade. Just get it to the thickness you want, then coat with several coats of a water-resistant finish and you'll be all set for years to come
 
Bigkat650 said:
Exterior grade plywood is where its at. Same glue that is used in marine grade, but the difference is it's not guaranteed to be free of voids--which is not worth spending 2 or 3 times the cost of exterior grade. Just get it to the thickness you want, then coat with several coats of a water-resistant finish and you'll be all set for years to come

The only problem with that is that you can't usually get the thickness you want...most boats need a couple layers of a thickness...for example two layers of 3/4" then you laminate (glue) those two layers together to get the thickness you need.

Also if you want to be set for years to come you can't just use any water-resistant finish, they are not created equal. Do not use spar varnish or spar polyurethane...if you are using spar use spar urethane.


As the past two posters mentioned, the exterior grade is perfectly fine, but I prefer a hardwood ply. The reason I prefer that is that my transom is entirely exposed in front and a nice oak (or other hardwood) is going to look a lot nicer - also it is harder than typical exterior ply. If you have an aluminum front that covers your transom or you plan on painting it than by all means go for the exterior grade - it will do you fine.
 
Jdholmes said:
Bigkat650 said:
Exterior grade plywood is where its at. Same glue that is used in marine grade, but the difference is it's not guaranteed to be free of voids--which is not worth spending 2 or 3 times the cost of exterior grade. Just get it to the thickness you want, then coat with several coats of a water-resistant finish and you'll be all set for years to come

The only problem with that is that you can't usually get the thickness you want...most boats need a couple layers of a thickness...for example two layers of 3/4" then you laminate (glue) those two layers together to get the thickness you need.

Also if you want to be set for years to come you can't just use any water-resistant finish, they are not created equal. Do not use spar varnish or spar polyurethane...if you are using spar use spar urethane.


As the past two posters mentioned, the exterior grade is perfectly fine, but I prefer a hardwood ply. The reason I prefer that is that my transom is entirely exposed in front and a nice oak (or other hardwood) is going to look a lot nicer - also it is harder than typical exterior ply. If you have an aluminum front that covers your transom or you plan on painting it than by all means go for the exterior grade - it will do you fine.

Well any water treatment, as long as it's done right--will give you at least a couple years of solid use. I agree not all treatments are the same.

But i'll be honest, I plan on using this boat for 1-5 years, and I realize no matter how much I put into it--i'll only get so much out of it when I sell it. I already know I'll have more into the boat just in material cost then what I can sell it for, and I'm going as cheap as possible--its how the market is. Not to mention the labor cost. Which is why im ok with Tompsons Water Seal... Its cheap, and I'll be able to get the use out of it I need. It fits my need better then a more expensive sealer.
 
You can go as cheap as CDX (about $25 a sheet) plywood or step up to a better grade like Aruco ABX (about $35 a sheet). The Aruco will look nicer and have a lot less voids in it for a more solid build.

Seal your wood with an exterior grade spar urethane, 4 coats. Your transom will last for a decade or more, maybe a generation if you keep it covered and out of the elements.
 
Thanks, Friends. And thank you for looking over the poor typing on my mobile phone.

I'll take your advice and not worry about "marine grade" wood, and seal some sort of fir, since I have an external metal brace.

Since I have not disassembled a transom before, what am I getting into once I begin ripping it out? Will there be holes in the back of the boat that need to be sealed or new rivets installed? Thicker the better?

I appreciate you taking the time to help.

RP
 

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