All depends what you want it to do. If you want to heat a 40ft based in Scotland and liveaboard all winter you need something different to if its a 26ft in Devon and you are only aboard May to Sept. Charchoal is also good in small sizes. From my experience and judging from post on here the last thing I would do is fit an eberspacher, lots of posts shoulting for help to get them working, they seem to be fiddly, critical and heavy on electric power and very expensive to buy and on service/spares. Add some more details for more detail replies