What's the difference between a Class 2 & Class 3 Hitch ?

As executive said, you need to be aware of all the ratings, of a vehicle and receiver. Travel trailers tend to be more stable at 13-15% tongue weight vs. other types of trailers. Some boats can be stable at 8% for example. So if you expect to tow about 3500 pounds of TT, then you need to be prepared for up to 500 pounds of TW. I believe the means you should be looking at class 3 receivers.