I have been looking into heaters for my new boat too. I have always been concerned about bulkhead mounted heaters on a small boat because of the risk of someone falling on it and getting burned.
Propane never seemed like a reasonable fuel
since it would take a big tank to heat the boat for a weekend. Diesel contains a lot of BTUs/gallon
Im trying to decide between diesel fired forced air heaters and hot water recirculating heaters. I think for a boat the size of yours the smalles of the forced air heaters would probably be the appropriate choice. The brands I have found are Espar, Wallas (http://www.scanmarineusa.com/Heatlist.htm), and Webasto (http://www.boatheat.com/)
The Wallas systems looked attractive because they use less electricity than the others but they are larger. the Webasto is about the size of a small car muffler and appears to be able to be mounted wherever you can find the room.
One of the major advantages of these heaters is that they can be mounted outside the livingspace on the boat and CO would be less of a worry. I would still get a CO monitor.
You can put one of these heaters in the lazerette and run a single duct to your cabin. You run the exhaust
out the other way. It does not have to go through a stack on the deck. I have seen boats where the heater exhaust
goes out through the transom just like the engine exhaust
These heaters are much more expensive than the dickerson and force 10 options but they have much greater output amd are reported to be less fussy to keep working. Any of the small forced air heaters could probably keep your boat pretty warm.
FOr my boat Im leaning toward the recirculating water type because it can also be routed through the water heater to make hot water at anchor
. Its also easier to run the automotive type heater hose through a boat than 4" flexible ducting.
One thing I did notice when checking out the heater on a friends boat is that the pump
that is used to feed the heater is very loud and I would find that sort of intermitant noise difficult to live with at night. I think a "day tank" near the heater is probably the solution I will go with.