Just wondering what the guys with experience would recommend for an adhesive. I have a floor that has gotten soft over the years where the original seat pedestals were screwed in. I tried reclocking and drilling new holes, but the whole floor in that area is soft. I know the proper fix would be to completely remove and redo the floor. Well that is not happening this year if ever. My boat is most likely only worth $7500.00 or so and most of that would be in the drive train so spending a bunch on reglassing the floor when I really want to upgrade anyway is not in the cards. So my plan is to sand the existing floor, get a 2x4 foot sheet of 3/4 marine plywood, run some countersunk bolt up from underneath to attach my pedestal to, and then glue and screw that plywood to the original floor, and then seal everything up with resin. My question is what should I use to adhere the two pieces of plywood together? Any ideas, I would love to hear them.
TIA

Epoxy!

You'll still have wet foam under there.....

Ayuh,... Plain ole water proof construction adhesive,.... Liquid nails,....

Any specific type or brand? Or just whatever I get at the big box store?

Thats what I was wondering, I have used the Loctite brand adhesive and the Gorilla brand adhesive, I just was not sure if there was something made more specific for marine use. I had someone suggest using resin between the two, but I was not sure that would work?

I drilled a few holes quite large to try and get some T-bolts in there and the foam seemed quite dry and hard (enough that I could not get the T-part to pivot). Even the soft wood was dry, just not enough there to hold onto the screws on the 8" base. The boat used to sit outside and I suspect the canvas cover combined with the glued down carpet just retained too much moisture for the floor to handle. Amazingly the floor is still fairly solid everywhere else. the cabinets and the rear bench seat box are a whole other issue.

Liquid nails "polyurathane construction adhesive". Resin will be too brittle and 5200 will be too expensive.

I wouldn't be concerned with to expensive on your bonding agent. Your talking about less then 100.00 to have a better product. However, If this glue doesn't hold your going down while the boat is underway. If you don't have a tether on it can be really bad for someone else out on the water or on land. If you don't want to cut the floor out and put a new floor down I understanf. What I have done very cheaply on a cheap boat to get a couple years out of it is this. Take out the seats. Cut 3/4" plywood to cover the whole floor all the way to sides of the boat. Cover the back side with some epoxy. When you go to put it down on the old floor use either 5200, or epoxy with fiberglass powder mixed in. This is a West marine additive that makes it more of a paste and better as a glue then a sealer. Just regular epoxy wouldnt work as well it is a resin not an adhesive in its normal state. Set the new board down in the boat and put screws into the good pieces of flooring to hold it down. Then fiberglass with epoxy up the sides of the new floor to the hull sides. This will give it a much more rigid feel and keep the boat and floor together as one. I would also do fiberglass and epoxy on top of the board then put carpet on it. This should cost you around 500.00. But will be down and you will have a better riding boat then you do now.

He is looking for a quick cheap fix, polyurethane construction adhesive (liquid nails) is just fine. Epoxy is not the answer here. Unless the floor mates perfect and prep is good I'm not so sure epoxy would do the trick.