I am getting started building a wood drift boat, and have been doing a ton of research. The consensus among the wood boat crowd seems to be a choice: Marine Varnish over epoxy sealer, or an oil finish. Plain varnish over wood, particularly gunwales (take some abuse), is likely to chip, flake, etc and need sanding and redoing often to look nice. An oil finish (Teak Oil, Penofin, equal parts Linseed Oil and Turp, equal parts Varnish, Linseed Oil, Turp, etc) will need to be wiped on a couple times per year, but no sanding, and will build up to a durable finish (soaks in rather than sits on top of the wood). Many old drift boats that have just been oiled a couple times per year are in great shape after 20-30 years. WoodCraft and Crosscut Hardwoods are two places to look. No perfect finish out there, Montana Boatbuilders forum and Wooden Boat People are a couple spots for more info. Re varnish, Man o war and helmsman spar are the lower end of the marine varnish field, but more available.
Michael