Suburban IW60 Nautilus Tankless Water Heater?

Can not speak to your specific question but i will point out, propane provides a maximum burn of 91,000 btu per gallon. consider how the run times will change how long your propane last as well as water availability.
If you are in an rv park with full hookups, you may love the "unlimited hot water"
Does the tankless offer any form of electric water heating when you have electric available?
Just points to consider.