We have an Espar fitted in our 1995 - 40.5, it was on the boat when we bought it. It is fitted in the port stern cockpit locker where once stood the genset that came with the boat but was removed by a former owner. It exhausts thru a thru hull on the port side just below the toe rail and breathes it's fresh air from the interior of the locker. Thermostat unit is mounted on the port side locker in the master cabin and ducting is under the bunk to an outlet in the master cabin then thru a Y connection into the main salon. It heats well, sips fuel and is easy on the home batteries. It is the smaller of the Espar units and I intend to up grade in the near future to the larger unit. All the present electrical, fuel and exhaust systems will remain the same between the two units.
