I installed a HeaterCraft heating system for my cabin in my 2000 30 Ft Catalina MKIII. This uses engine heat while motoring to produce cabin heat, similar to a car heater.

This is an easy installation with clearly written instructions provided by the manufacturer.

Step One - Cut a hole for the heater vent. Be carefull to select the proper placement of the vent per the manufacturers instrutions.

Step Two - Mount the heater.

Step Three - Wire the heater to 12 volts.

Step Four - Plumb the heater hose inline into the path of the hot water heater.