Look into the Aqua-Hot 375-LP unit. It is a propane fired hydronic heating boiler that also provides endless hot water Tankless) when connected to city water.
It is an expensive unit but will do a superb job of heating and hot water production from one unit. It also has an electric element for water heating when connected to shore power.
Lew Farber...RVIA Certified Master Tech...ABYC Certified Master Marine Electrician
SOLAR TECH ENERGY SYSTEMS, INC.
AM SOLAR ...MAGNUM…VICTRON ENERGY...LITHIUM & LIFELINE BATTERIES…MARINE REFRIGERATION