If you're going to be tied up at a dock where electricity is available, why not buy a decent quartz heater and just plug it in when you need it. It's a clean source of heat, requires no ventilation, and is inexpensive to buy. This will also allow you cut way down on your propane use.
If you're away from the dock, your propane heater should work quite well for you. Your propane stove is little different than the stove I'll be cooking on tonight and is almost maintenance-free. So, why change it out?