We had a Force 10 Karosene heater on a 33 foot boat that did a nice job of taking the chill off on cool mornings. The tank we had needed to be pumped up with a bicycle pump to pressurize it and the burner needed to be pre-heated but it was pretty simple and reliable. Installation was not too hard mounting to a bulkhead and a flue pipe going through the the deckhead. The only problem is they don't seem to be available any more.