Agreed, but if you are going to all that trouble, why not use one of the Dickinson diesel bulkhead heaters. I recognize that reasonable, rational people can look at the same data and reach different conclusions. From my perspective, the energy density of diesel is higher than propane, the cost / BTU is lower, you end up with fewer propane connectors inside the boat, and fuel capacity on most boats is substantially higher.
I guess my earlier point was, moisture is not an issue with these units.
As for the pros and cons of diesel vs propane as a heater fuel -- we've hashed that out quite a bit in some of the other threads. A strong case can be made for both, in my opinion.
But briefly, in defense of propane:
-- Only one propane connection inside the cabin, and that's at the appliance. The one other connection is in the sealed, vented propane locker. Diesel has multiple connections (at the tank, the pump, the appliance) increasing chance of leaks/odors.
-- Virtually no maintenance on the propane units. Diesel units require more cleaning/maintenance.
-- Propane burns cleaner. Diesel can leave a soot/residue on deck and occasional odors.
-- Propane can get away with a 24" flue height. I forget what the measurement is for diesel, but to achieve proper draft, flue length needs to be quite a bit longer. This is not a problem on some boats, but on others it can be tricky.
According to Dickinson, the Diesel Newport heater requires a 48" minimum flue length. That works in some boats, but is very problematic in others. Usually resulting in a higher profile on deck.
-- Lower power draw with propane (just the remote solenoid). Diesel has an electric fuel pump (admittedly, not a huge draw, but the propane can run with NO power (by-pass the solenoid) whereas diesel must have it.)
-- Simpler propane installation. No wiring necessary (unless hooking up optional fan). Just a single propane line from locker to appliance. Diesel requires a fuel line as well as a wire run to the fuel pump, plus a place to mount the fuel pump (in addition to the appliance.)
Also, the flue stack for diesel requires a 5" hole in the deck, whereas the propane flue requires "only" a 3" hole. That results in a hole nearly 3X the size. Drilling these holes is the scariest part of the installation.
-- Lower initial cost for propane appliance because there are fewer components.
As for fuel reserves/consumption - I guess it depends too. You're right though, diesel offers better btus and most boats have decent tankage. But for weekenders/vacationers with reasonable propane capacity, these propane units are very frugal too. We only carry 20 lbs propane, still it has not been an issue at all.
Again, the intended use is important here. For long-distance voyaging or living aboard, diesel is a very compelling fuel choice and I'd say the scales tip for it. But for weekending/vacationing, propane has many merits too.