Charcoal picks up moisture from the typical boat environment
and becomes very hard to light or keep lit. Doubt if you'd be happy going with charcoal.
Don't know how much you plan on barbecuing, but the small throw away bottles for stoves can be stored in an air tight container made up out of PVC piping. The small containers aren't much of a safety
issue, in any case, as their capacity is so small that a leak in one container or even several shouldn't reach explosive concentration. Used these small containers in a single
burner stove and lasted a long time for that type of cooking
. Most of what I'd be grilling would be fish
and that doesn't take long to cook unless you are the type that insists on turning good protein into shoe leather.