Re: Transom wood for my aluminum boat
I recommend using 3/4" exterior plywood on the inside. As mentioned, the Arauco ply is real nice stuff with virtually no voids. My local Lowe's carries it, but any exterior grade will be fine. For the outside piece........on my larger (16' and 18') aluminum boats with permanently attached motors, I eliminated that piece. It serves little purpose and is just a possible source for future leaks as the woods compresses over time. For a little boat where the motor may be removed/replaced often, I can see the virtue of having that piece on the outside to protect the aluminum. I'd try to find something non-wood to replace it with. Plastic cutting board, piece of diamond plate aluminum etc are possibilities. For sealing the wood, you can either use polyester fiberglass resin with fiberglass or epoxy resin with or without fiberglass. Poly has no strength by itself so don't try to use that alone as a sealer. I have personally used epoxy for mine. You probably won't find a suitable epoxy at a local place and you'll have to order it from somewhere like U.S. Composites or Clark Craft. Epoxy isn't UV tolerant so you'll want to paint any exposed parts of it. Rustoleum would be great for this.
Is your boat like this one?
http://i176.photobucket.com/albums/w200/ezmobee/DSCF2577.jpg This one is my dad's and is also a Sears (made by Alumacraft). It's a great little boat but it's only rated up to 15 and I would NOT want to exceed that. Transom strength isn't the issue. Weight, low freeboard, etc are. We actually run ours with just a little 4HP and while it won't plane, it move along really well even with 3 adults aboard. With a 9.9 it would go great. 15's are just about always the same "form factor" if you will as the 9.9's from most manufacturers so I think you could safely go that high. Forget about a 20 cuz it would be too powerful and too heavy. Now my uncle has a different 14' Sears and his is higher sided and heftier than ours and if yours is more like his, you can ignore the above advice (however he uses a newer Merc 9.9 on his and it also hauls).
