I agree with sky-guy. A 16 footer will probably serve you best.

As a kid I fished with my dad off West Point and Elliot Bay in a 14 ft Aluminum boat. These are a little more protected waters than off Possession. A 16 should give you a little more security and flexibilty.

Keep your eyes open for good deals. Lots of boats tis size move around especially after salmon season and it starts turning cold.