Tom, this might be an alternate.

A fried of mine got tired of his treated plywood front porch rotting
out in three years because it's really exposed to the weather. his home
sits facing the west, so it gets the summer rains, winter snows, and
scalding summer sun.

about 10 years ago, he bit the bullet and replaced his deck with
synthetic material. Actually, it's like you were saying about the sign.
resined wood. It's lasted for 10 years and looks and lasts so good,
he's thinking on re-working his Pontoon deck with the same stuff,
seeing he has several boards left over. I assked him about carpet, and
he then asked me."What for"

http://www.decks.com/article50.aspx

Of course as I write this he hasn't doene it yet, but I really don't
see why a person couldn't.

Good Luck!

Tim



Tom G wrote:
I'm replacing the carpeting and a couple of rotted deck boards on my pontoon
boat. Marine plywood is pretty much hard to get around here but I can get
MDO plywood (Medium Density Overlay) which has a resin impregnated (Paper?)
layer on each side. This stuff works great for outdoor signs, etc and lasts
virtually forever. However the carpet guy is telling me that the carpet
adhesive won't work with it because "nothing sticks to it". I've queried
the mfg of the adhesive and they don't seem to have a good idea of what MDO
is either. The carpet guy even tried to tell me that paint wouldn't stick
to it. Years ago I had a commercial outdoor sign painted using it and it
lasted for years with no noticeable weathering or paint loss. So, has any
one had experience using it and applying carpet or glue to it. The Exterior
plywood I've found is really bad quality.

Tom G.