I took a diesel heater (out of the trash on Tangier,Is.VA june07) and cut out the fire box,kept the glass door and welded a steel 3/8" fire box ,
made a stainless ash tray and cut up a couple of cast iron grates from a gas grill someone was throwing out, so I could burn anything from coal to driftwood.
went to the scrap yard bought a 12' lengt of food grade thick wall 3" tubing ($12)and made a flu. bolted the stove to the forward bulkhead w/ a 6" standoff. took out a port so I didn't have to cut a hole in the cabin top.
works great! every time I used it I would anchor next to really expensive yachts and laugh at them while they froze ! I would would say stuff like "oh, you mean your Beneteau doesn't have heat?" an then invite them aboard to thaw, they always brought good wine or booze. great investment.