Needing to replace the decking on my pontoon boat, I made a trip to the local lumber yard. I found that there were as many different materials to choose from as there were colors in a rainbow. I am a novice at this, therefore I asked a lot of questions. Most of the employees there knew less about marine grade plywood than I. I then went back to the Internet to do some more research. Upon learning what I thought might be enough to talk about the subject, I headed to a marine repair shop near the lake. I thought they could probably steer me in the right direction. I specifically asked about replacing the deck on my pontoon boat. I was told not to buy marine grade plywood because it was "way too expensive". I was also told to go to a specific lumber yard to get the kind of dry treated plywood like they used when replacing a customer's deck. How could I go wrong by using the same product the "pros" used?
After purchasing the plywood the "pros" use, I returned home to start my project. I bought a gallon of water sealer and put it on both sides of all four pieces of plywood. By the time it dried, the weather turned cold and it started to rain. I covered the plywood with a tarp. It was several weeks before I could get the time needed to start replacing the deck. When I inspected the plywood, the layers had already started separating. How was this plywood, recommended by the "pros", going to withstand years of use on the deck of my pontoon boat? I called the supplier and told him what happened. He told me that he had gotten a "bad batch" of plywood and would replace it with new. Okay, I guess that could happen. I'm only out some time and a little water sealer.
I started my project by removing all the deck furniture and fixtures. I labeled all the wiring and made a template to help me relocate and reinstall everything. Again, cold and rain set in and I was forced to postpone the project. The rain was to my benefit because I found the "new batch" of dry treated plywood showed signs of starting to separate... again! Forget this! I'm using the best I can buy. I ordered marine grade plywood, 4'x8'x3/4". I've never been sorry for that. If I would of used the dry treated plywood, I would have had to replace the deck again in as little as two years. Lucky for me, my project was delayed and I saw what the wood was doing before I installed it.
I told a friend of mine this same story and he related his experience with marine grade plywood to me. He helped his Dad replace the floor of their old aluminium boat in 1972. He replaced the floor in the boat again about five years ago. It had lasted more than 30 years because his dad insisted on using marine grade plywood then. You can bet I'll not start another decking project without it.