Underwater loan

Here's another suggestion. See if anybody in your area has a motorhome rental company. Sometimes they accept privately owned motorhomes into their fleet because it keeps their capital expenses down. Make sure you check with your own insurance company before doing this to make sure it's covered. Let the private company rent your motorhome out and hope to make enough money to cover the payments. It's going to get trashed as a rental but you aren't using it anyway. And maybe you'll luck out and one of the renters will total it for you and the insurance pays off the mortgage. (Make sure you have insurance that covers the full loan on the motorhome and not just the value before doing this.)

You can even rent it out yourself by putting ads on Craigslist, but again make sure your insurance company is okay with that. You can require that renters provide a rider under their own insurance to cover any damage. I had a friend that rented out his own motorhome most of the year and used it himself part of the year and the rent money made the motorhome basically free to him. I couldn't do this myself, but in your situation it may be a good deal for you.