George,
I'd say 1000 or 1200 on that Float-On trailer. It might be rated for 6000lbs, but i'd bet it has 3500lb torsion axles. it's the same trailer my buddy in CT has under his 20ft Robalo except it's a little longer. His has 3500lb axles, but only has 6000lbs worth of tires. 205 x 14's at 1480lbs each. 215's would give you another 200lbs each.
Funny, lightening hit a pole and powerlines fell across it and it cooked the tires off it along with the rubber in the torsion axles. Insurance paid for new axles and tires. The axles came from Float-On in FL and they were 3500lb axles. The trailer is way over kill for a 20ft Robalo so he stayed with 205 x 14's..
That's how I know it has 3500lb axles. That and I've never heard of or saw a 3000lb torsion axle.. But you have to figure the weight of the trailer, about a 1000lbs into the deal to figure it's real carrying cap...