I went digging and found that Bosch now offers a unit - the RV500 - which they claim is the "only one" approved for boat and RV use. Promotion aside, it appears they have come up with units that they say are "approved". I would still check with your insurance underwriter. Unfortunately, it is always easier for insurance companies to say no, but installing without notifying may leave you exposed. I'm not an attorney. Seems everyone else in the USA is.
"We have met the enemy and he is us." - Walt Kelly's Pogo