Guys, make your own mind up regarding whatever floats your boat. Personally, if it's not rated for marine use, it serves no purpose on my boat.
I'm not a Naval Architect, but being a building architect, I've seen what can happen to so-called "exterior glue" plywood when directly exposed to the elements for a while. It warps, buckles and delaminates . . . regardless of that label. You never know when the cabin may take on some water.
Hate to use the overused cliche' "penny wise, pound foolish" . . . but it holds true with plywood. Use only marine rated plywood, with mahogany core plys on boats. Anything else is a serious compromise and not worth the $30.00 to $50.00 +- savings.
Edit - I forgot to mention that pressure treated plywood contains high levels of arsenic. Not familar with boat-building use regulations with this stuff, but in building construction practice, It is illegal to use PT wood indoors without the ability to ventilate the outgassing of poisons.
Last edited by TrueBlue; 02-13-2006 at 08:56 PM.