Greg,
I have the Mr. Heater Little Buddy on my boat. It works great.
Haven't had a problem with Carbon Monoxide. I've got Carbon Monoxide
detects onboard and they've never chirped once while running the heater
all day and night. I run mine off a 20 lb tank. Running it on high
when I get home from work until the next morning (about 14hrs) I get
about 4 days run time out of the tank. The manufacturer states that it
will give 50hrs run time on high and 100 hrs on low off a 20lb tank,
and I have found those figures to be pretty accurate.
I can tell you this, that one Mr Heater Little Buddy heats my boat
much better than my three built-in electric heaters on the boat. It
also helps take the dampness out of the air, which the electic heat
didn't touch.

Dan
M/V Sea Ranch