Decided to replace the decking

[warddog]

After some thought and suggestions on here I have decided to go ahead and replace the decking on the pontoon I am replacing the carpeting on. This is a 1990 Playcraft that has rails in which the decking is sandwiched in between what appears to be an "E" shaped rail. The bottom is bolted to the toons and the decking is crammed between the top like an "F". Having to remove the rails where the decking is sandwiched, I have found them to have some kind of black sticky gasket material between the rails and the toons. Anyone know what this is and where I can find it to replace when I put the rails back on. The bolts also appear to have a white hard plastic type of washer on the toon side, that probably need replaced when put back together. Anyone know here can those be found as well? By the way the decking was also caulked into the channels of the rails and curious what may have been used to do that as it was still pretty tight in there after all these years?

 

[Scott Danforth]

the plastic washer is a galvanic isolator between the stainless fastener and aluminum. get garolite washers from McMaster Carr

the black sticky stuff may have been 3M 4000 UV or other elastomeric sealant

 

[captmello]

on mine, there was black butyl tape on the crossmembers where the plywood seams were. apparently to keep water from splashing up and through the seams.
Not sure you need it if you're just making a floating raft. I was able to source the old style treated plywood, non corrosive, at a local marina. No sealing or treatment necessary.