I finished installing a Wallas 40D diesel furnace in our P42. The unit is installed in the port side stern main deck locker, mounted on the magazine cabinet bulkhead. Seemed to be the best place considering it was close to the stern and the fuel tank, plus it can draw intake air through the opening into the quadrant well that also supplies air to the heat pump. I surface mounted the control panel on the aft cabin port side bulkhead just below and to the left side of the magazine cabinet. I used a three inch hole saw for the registers and a three and one quarter inch hole saw for the ducting.

Everything is connected: fuel, power, control panel, exhaust pipe and warm air ducting and registers. The dealer advised to install the system before ordering the exhaust pipe and sock because of its high cost. One duct and two registers are located in the aft cabin at the base of the double berth, with another duct with two registers in the main cabin port side setee. Since we do not plan on installing a washer/dryer combo Im going to use the engine compartment vent duct route for part of the warm air ducting.

One duct runs behind the rudder post to registers located at the base of the berthing cabinet port and starboard side. This has worked out pretty well because I can direct heat into the aft head. I installed two registers at the base of the port setee and one under the navigation station.

The new furnace has made a huge difference in cabin comfort for the admiral while on the hook. The system is quiet, efficient and really pumps out the heat. Cold weather comfort should make a big difference during winter cruising.

11/2014 Update: Installed the Wallas 40D diesel furnace in March 2006. Have not touched the unit since then, but have used it many times to keep the interior warm during our winter cruises. Simple to operate, thrifty fuel and power consumption and quiet. Unless there is below freezing temperatures outside, a middle thermostat temperature setting is sufficient.

1/2015 I also used the warm air duct blankets similar to the foam plastic used to insulate water pipes only larger. I wanted to make sure as much heat reached the registers as possible.