Alignment? Is the axle 90 degrees to the frame? Do the tires wear evenly?
Any sign that the trailer has been damaged in some manner in the past and repaired?
What happens if you tow the trailer empty without the boat?
Tires look good, nothing stands out except that the bearing were trashed on one side and just fine on the other.
No sign of damage either. Couple of tiny dents on the wheel wells and that's it. Everything else looks true.