Replacement Deck Plywood for Aluminum Crestliner?

[fishrdan]

I have an 18' Crestliner Super Hawk that I'm replacing all the deck plywood while changing to a vinyl interior. The original 1/2" pressure treated plywood is in good condition, but thinking of replacing it with 5/8" or 3/4" since there are a few broken out places because of thin cuts. Is 3/4 to thick and heavy for decking?

Last year I picked up a few sheets of 1/2" ACX 5 ply plywood, but it's no longer stocked at the big boxes, go figure... Lowes sells Arauco plywood that has thin plys, bonded with exterior glue, is pretty rigid, supposed to be void free and has a nice face veneer, so it seems like it would work well for a boat deck. One thing that is odd, even though they say it's suitable for exterior applications it does not have an ACX rating? What do you think of Arauco plywood for boats? Should I look for ACX elsewhere or spend the cash and go pressure treated?

The boat deck has gaps along each plywood panel and a few vents in the floor, so I'm not going to seal the bottoms of the deck panels,,, allowing the plywood to breathe and dry out. I don't know if this is a wise decision, but the 7 year old wood is in good condition. I guess this is the way Crestliner designed the boat. I live the desert and the boat will get baked on a daily basis

My previous fiberglass boat had rotted decks because of water intrusion in the sealed deck, so I'm trying to avoid water getting trapped in the deck plywood of this aluminum boat.

 

[Joe_the_boatman]

Re: Replacement Deck Plywood for Aluminum Crestliner?

I used pressure treated 1/2" in my 18' aluminum Starcraft. Some areas needed to be reinforced to keep from flexing, like around the bilge, and near the bow. I wanted it to be as light weight as possible though, so I don't regret using 1/2". 3/4" should be plenty stiff, but at the expense of weight.

The underside of my deck is bare, also. The top was primed and painted, and like yours, there are gaps around the sides to let it breathe.

For what it's worth, the original deck in my boat was untreated 1/2" plywood covered in vinyl. It was black sawdust when I got the boat - I used the shop vac to get it out. I wouldn't ever use non-treated wood in a boat.

Us guys w/ aluminum though have to either insulate the ACQ (post-2003 preservative) from the aluminum (I used epoxy), or you could buy the CCA (pre-2003 preservative), which is still legal for marine use. "Marine plywood" uses CCA for this reason. The copper in the ACQ reacts w/ aluminum and eats it. Just check a galvanic corrosion table.