I have seen several pics over the years of people trailering their motorcycle on their boat trailer. I am not talking about a third trailer, but an extension on the boat trailer so you can trail the bike perpendicular to the boat.
One example is from Neil Fett (bigasswake)
I am planning a two-month trip from Indiana to California hitting up at least Lake of the Ozarks, Powell, Tahoe, Lake Havasu, and maybe Shasta or any other cool lake along the way, and would really like to bring my dirtbike.
If anyone has any ideas on how to get my bike on the back of my trailer, please fill me in.
Thanks