I have a Balmar 120 diesel fireplace. Balmar, of course sold it under their label, but didn''t build it, nor do they sell/support it today. However, the unit is still being manufactured under Sigmar Marine (http://www.sigmarine.com). It is a diesel fireplace with a balanced draft set up. The balanced draft is a nice feature, in that it draws its air from outside the boat, thereby eliminating carbon monoxide problems as well as blow outs from down drafts. Diesel is gravity fed direct from the boats main tanks.
I''ve had great luck with it, although soot needs to be cleaned out of it regularly to maintain quality operation. As long as I have diesel in the fuel tanks, I have heat. Keeps the cabin of my 32 footer nice and cozy during colder winter months. The fireplace and its shiny, 3 inch brass flue are focal pieces in the salon.