I think you are better off with either marine or diesel oil. Boat engines run a lot cooler than cars so as I understand it there is a different formulation of additives that help prevent rust vs. additives you need for a car. Sure it might cost a little more, but there are differences vs. auto oil. I'll second the Napa gold filters though, I use them on all my vehicles and they seem to be a quality filter (expecially when compared to Fram or some other cheap junk).
Just my opinion, but with the cost of the boat I'd error on the side of giving it the right stuff.