Be sure you have a tow capacity of 3500lbs.
My 2 tow vehicles do, BUT that includes everything IN the tow vehicle, except the driver, too. So if I've got 3 passengers w an average weight of 200lbs, and 300lbs of gear in the SUV, I've only got 2600lbs of actual tow capacity.
Call your local recycling yard. As long as there isnt a line for the scales, I can drive across them w the boat and trailer, drop the trailer and move my SUV off the scales. Once weighed, I leave then come back w just the trailer and after subtracting its weight from the combined weight I get a good estimate of boat weight.