Our heater is deisel but the idea is about the same.
The heaters are safe provided you follow the installation
manual. You'll need a chimney for it with a proper deck
fitting. I have a cap I attach after I pull out the normal cap. I can't sail with the heater in operation and would suggest you not do that either. They make metal shields to attach to the bulkhead as well as a standoff so the distance is appropriate for the heater. You don't need any insulation
. The shield attaches with small screws.
You want to get a Carbon monoxide detector. That is the real danger
not losing all the oxygen. Carbon monoxide will kill you in your sleep. You do need some source of fresh air but it's not a lot. There needs to be a draft
up the chimney. Your boat may already have enough venting that you won'yt need it.
Note that when you burn fuel
the proces yeilds cabon dioxide and water
. Imperfect combustion may yield soot and carbon monoxide. No proces is perfect but a well adjusted heater should never smoke. Most heaters take some manual adustment after you get them started. You need to learn how to do this based on the type of stove.
If you have the specific brand and model perhaps somone here has installed the same unit before.