Re: 14' aluminum boat seats- what to do
Hello again Kid. There are several ways you can seal the wood in your boat. The "best" is probably to use spreadable, 2-part epoxy. Once cured you'll then need to apply paint/cover to give the epoxy UV protection. It works great, but it can be a little pricey and you'll have t track down the epoxy itself from West Marine, US Composites, or similar source. You can also use fiberglass mat and wax-free resin (not the stuff you get at the auto/home improvement store). It works great, but kind of messy if you've never used f'glass before. A great third option is to use several coats of Spar Urethane. The nice part about spar is that you can get it at any home improvement store and you can leave it clear to show any wood grain. You can also simply paint the wood with several coats of old school, Rutoleum, Professional, oil based enamel. It won't exactly waterproof the wood, but you will still get many, many years of use out of it.
BTW, NEVER use pressure treated wood in and aluminum boat
Instead, get the best non-PT, exterior grade plywood you can.
As far as the foam goes, while there are several options, the simplest, cheapest, best is to use the pink/blue closed-cell insulation foam board from lowes/HD. You can simply cut it to shape and use it fill and cavities in the boat. The more the better. While the foam won;t keep the boat from getting swamped in big water, if should keep it above the waterline so you can bail it out, if need be.