I don't coat the whole board. In the case of a 2x6; I coat about 70% of the flat side of the board.
My Myco was 4 seasons old when I got it, and the wood was JUNK. I mean it was falling apart; all splintered up and cracked. I started from scratch (beginning of this season) with all new 2x6 PT Grade A Pine. I consulted a buddy and OSO member who owns a Cypress mill, and he said just use PT pine.
IMHO and experience, leaving the bottom/back side of the wood/board/bunk open is the most important factor to allow for drying. My Myco had black carpet over 80% of the board, and exposed wood was then coated with black paint for looks. I did NOT repaint the back of my boards when I redid everything.
See this thread on SOS:
http://www.seriousoffshore.com/forum...arpeting+bunks