You know something else you might want to consider? Getting an old VW Westfalia van. I had a roomate that was nuts over these things and I helped him rebuild two of them. They can be had relatively cheaply (although some folks are very fanatical about them) and as long as you find one that is water cooled (I think post 1985 or 1986) it could be quite a regatta mobile. I am quite sure that the air cooled might have a problem towing a catamaran (and the heater sucks in the wintertime).

Here's an ebay link: Ebay Westfalia Vanagon serach

on second though...holy crap...those things are STILL expensive for a 20 year old one!