I just checked Newmar's archives. They list ONLY a Standard 10 gallon water heater or the upgrade optional Oasis type LP powered System hydronic zoned system.
So, that points to one of the problems with forums. The OP has just purchased a 8 year old Motorhome and has questions. BUT, he has no way of knowing what the previous owner/s did to that coach. They may have added a Tankless system and wired it in such a way that it does indeed stay on when he thinks he has turned it off. When he checks, he will post the Brand and hopefully model of his Tankless system. We can then give him more accurate info. Doug