Axles
A pair of 3500 lb axles are too light: TJ's post said he used 6000# axles & I agree totally. Your 6500# boat + trailer is going to gross out >8500# and for a longish tow in warm weather, the bearings, hubs etc on the 3500# axles are going to be overloaded. Make shure you've got good effective braking on both axles, and that the tires are rated for the load & inflated to the max. recommended pressure. Even if your tow vehicle is a 1 ton dually, the trailer suspension, brakes & tires are going to make the difference in handling & stopping safely.I hauled my boat abt. 300 miles : gross wt was abt. 9000# & I had 2-3500# axles on the trailer. Even tho the ambient temp was c. 30°F, the trailer bearings were pretty warm. I stopped every 1/2 hr or so to check them. If it had been summer, I think the bearings would have overheated & failed.Max. vertical clearance on major highways is 13'6", but watch out on any secondary roads as there are often wires, cables etc that are lower. You can do it & good luck to ya, but don't shoot yourself in the foot by cobbling up some mickey mouse trailer that'll leave you stranded in the Mojave.