We use a Zodi Hotvent Tent Heater on Dauntless. The propane heater remains outside the cabin and the cabin air is recirculated through a heat exchanger without ever mixing with the exhaust gas from the combustion chamber. I made a special weatherboard that has 2 3" ports in it. One port has an aluminized 3" hose that goes to one side of the exchanger and the other is the return. The unit uses a 3" 12v blower fan to circulate the air. Works really well down to about 35 or 40 degrees, at which time the propane bottle starts to loose too much pressure due to the outside temp and the efficiency of the burner really suffers. We did spend a 20 degree night on the boat last year at a race in Phoenix (remember that Gary?). The heater was only able to get the cabin up to the low 50's and devoured a bottle of propane every two hours. But that low of a temp is very unusual for us. Anytime it has been in the 45-50 range the heater worked great. It sits on the floor of the cockpit. We always use a CO monitor inside the entire time the heater is running just in case there ever was a leak. Since no combustion is occurring in the cabin, moisture condensation (water vapor is a by product burning propane) and Oxygen depletion are not a problem. And of course....as per the instructions that come with the heater...the lawyers say that you should never use it in the manor that we do with everyone sleeping.......So ........Don't ever use a Zodi heater in the manor that I just described unless you want to wake up dead! Here's a link to their page: _http://www.zodi.com/web-content/Consumer/zodihotventhp.html_ (http://www.zodi.com/web-content/Consumer/zodihotventhp.html) ************************************** See what's new at http://www.aol.com