We installed a Wallas 40D a couple of years ago in our 40' PH. It has run extensively since that time with no issues. We did the install ourselves with great support from Scan Marine. We used the heater during a nasty winter storm when the shore power was out for five days, the temperature was in the low teens at night and the wind was blowing a steady 35 knots and the boat stayed in the 60'sF. Very happy with it, and the power draw is quite low (and so is the fuel use).
SV Laurie Anne
1988 Brewer 40 Pilothouse