Hi Steve!
Weathering a boat is about the same as weathering an AFV, with one difference...sailors take very good care of their girls, mate (and I'm not talking about our better halves

), and if it doesn't move, was usually painted and re-painted to preserve longevity... as far as any heavy weathering, well, not so in most cases...battle damage can be shown, but usually, the shipmates were/are still kept busy in downtime with repairs and refinishing...
SO, with that said, a light wash to accentuate the fine lines of the boat is really all that's necessary, unless you want to show the boat in a heavily used state, such as in the throes of battle, then you can still utilize the same weathering methods as you would in armor...take a look at some of Alan McNeilly's work here in the features dept, he is a master at showing his boats in the used state, very convincing, and very well done...
How to weather your boats (Pier 51) The Boats of Pier 51 Landing Craft Trio Take a look around at the other ship models in the gallery, and then decide on the amount of weathering that you may want to show on your model...usually a little smut and rust in a few key spots is all that you'll need to make a convincing "in action" build...hope this helps ya out a bit, mate, good luck, and Keep Modeling!
~Gunny