Wabasto is the best way to go. I have been searching and new they are closer to $3000.00, unless I am getting hosed. This is what I am going to get. Not sure if you know, but propane is heavier than air. It can sink into your bilge and blow up with a spark. It does happen. Now that being said, be careful when you use it. I used to use those small bottles and when they get low they would blow out the heater and not stayt lit. They would not have enough pressure to close the built in valve at the top of the bottle when you replace it. Make sure and keep the little white cap that goes on them and put it on when done or empty.
My wife pulled the trash out of our boat one time, at the ramp, and put it in the cab of the truck. There was a small propane bottle in the trash. When I got back in the truck the whole cab was full of propane. I had to let it air out. This is how I figured it out. I switched over to the low profile pot belly tanks for now. Work great, but propane is dangerous.