2010, F250, 60,000 trouble free miles, 13mpg in town 16mpg on the freeway unloaded, I got 14mpg round trip going from MN to CA hauling back my new used 2001 205v... punched the cruise at 70mph and let it go... up and down those mountians was nothing for it, great engine breaking down hill, effotless downshifting up the hills.... change oil every 5k, and fuel filters every 10k and add coolent additive every 20k if needed.
If you are buying used those three things must have been done or you are asking for trouble.
I would like to get a newer one with better milage but I can't get a $10+k payback in the life of the truck just based on fuel. Note it is all STOCK. I don't think you need to have 850ft/lbs of tourque to tow most boats... my 650ft/lbs does a tremendious job with 3:55's in it.
you could always buy a HUMMER H2 or a F150 Raptor those would tow petty well too I bet