Re: welding and welder options
Look into the welding capabilities of acetylene alternative fuels.
I do a lot of brazing using Chemtane on a converted oxy/acetylene rig. Chemtane is LP based (but burns more like acetylene) and is a lot safer to handle. It goes into standard LP tanks, which would make it easy to handle on a boat. Since I don't do any welding (just brazing) I don't know if it is suitable.
Wouldn't a small inverter machine like the Miller Dynasty 200 do the trick? It is a TIG machine that can handle aluminum or steel. Since one of the primary welding jobs on a boat would be making new pulpits and railings TIG seems like a much better choice than MIG. It looks like it could even work pretty well for thin tubing on a 115/30A circuit, something that is easy to find at marinas.
boats that I sail on regularly: Pearson 28-2, Rondar 505, Yankee 30, Blanchard Junior