White74, what stove are you burning anthracite in?
There has been discussion of anthracite in this thread, though most people seem more familiar with wood and charcoal. The currently-made stoves that I'm aware of won't handle coal. Instead the makers tell you to use charcoal or wood, I assume because of hard coal's high burn temperature. My take on that is, it's a BS excuse to make a weaker product--the coal stove isn't exactly new technology.
I can't see trying to heat a small boat in cold really cold weather with wood. To me, a solid fuel stove that won't burn coal is impractical, unless you want to spend half your life sawing up wood and dumping ash.
I have a home made stove using boiler nuts aka anthracite
the design is heavy cast sewer pipe with air intake on the bottom and chimney on the top I lined the firebox with a fire brick insert and high heat mortar
the fuel is fed from the top and a clean-out on the bottom
the grate is 2 sewer grate one fixed one movable to allow for shaking clinkers out
all parts are cast iron
no window to watch the pretty flames
all connections are flanges with nut and bolt ( gasket )
long burn time and start up time
weight of stove is heavier than steel models
fuel cost and availability
lot of heat
small fuel storage
hot water built in
intake air supply is from outside
burn rate is controlled by butterfly in fresh air intake pipe
my chimney is wrapped in copper tubing for water heating going in and out to water tank using natural convection and heat shield with 2" space around whole unit
if you had the inclination the whole thing could be made up at your local foundry
If anyone wants to see design plans i could send them just pm me