Obviously, if you're going to be using the heater every day for months if not years it's not a good choice and an installed heater would be the thing to get. But,, If you're looking for something that you will use occasionally it seems rather silly to spend the money to install a marine heater just because you're a real sailor and that's what real sailors do.

When we were cruising Southern California and the Channel Islands the Mr. Heater was perfect. It took the chill out of the air on a 45 degree morning and warmed up the boat in the evening. Hell,,, we were in Rhode Island with sub freezing temperatures for a week before heading south and again it worked fine. Never had much of a problem with moisture.

Now,,,, If I had and lived on the boat in New England or the Pacific Northwest it would be a different issue. Instead of a propane heater I'd look for a diesel heater. Propane uses too much fuel to be of much use for any length of time and when cruising you don't want to continually look for and lug propane. Better to use the big tank the boat comes with.

Again,,, I'm not one to spend a lot of money on a heater,,, I'd rather go where it's warmer.