You counting the trailer weight? Fuel in tank(s)? 4000lbs seems a little light to me...
I tow my 17' CC with my 1993 Dakota with 3.9L v6--different model year styles I know, but I do also have all the towing bells and whistles: long wheelbase, 3.55 gears, posilock. Total load is 2800-3000lbs depending on gas level, ice, etc.
I would not tow anything any larger with my truck. Granted, I do not have trailer brakes...if you have trailer brakes and the other goodies, then maybe. And yeah, the v8 would definitely help, I ain't winning any races with the v6 while towing.
If it was me, and I was planning on towing any faster than 35-40mph (i.e., freeway), I'd get a full-sized truck with v8 to tow that boat.