posted 04-09-2011 11:36 AM ET (US)
If you're buying the boat from the dealer, combine the book weight of the boat, the weight of the engine and the weight of the trailer (provided by manufacturers). Add 700 lbs (or so).Seek a vehicle with a GCVWR that is 500 lbs greater than the figure above plus the curb weight of the vehicle.
Pay NO ATTENTION to the "tow rating" of the vehicle. You want a vehicle that can comfortably tow the rig, plus 500 lbs of you (passengers) and fuel for those trips.
Also - for added safety, you may wish to insist that the trailer sold with the boat come with brakes. In some states, there may be legislation that mandates the use of trailer brakes (depending on the weight) and the vehicle you choose may have a rating that is dependent on the trailer having brakes.