Might try the Troy DPW on Rochester south of 18. They have a scale with a readout on the building. I have taken a couple work vehicles there, but might want to call before you take a boat. Not sure if they would
I would figure there has to be one closer though...
the scale @ troy dpw is on 24 hours. just go at night or in the evening. stay to the left when u pull in and you will see the lane for the scales, make a u turn in the parking lot and pull into the scale lane. weigh each axle of your vehicle by comming to a complete stop on the steel pad and reading the eletronic display mounted on the side of the building. i really do not think anyone would mind.