A recent discussion on the Origami mailing list concerned the use of MIG vs. stick welding. The general consensus seemed to be that stick was preferred for their boatbuilding application due to ease of getting a good weld, and the ease of finding materials/equipment in out-of-the way places. Brent Swain has also made instructions available in the past for building a stick welder yourself out of just a few components.

For on-the-go repairs, a couple of solutions were tossed out, with different people liking the equipment. Might be worth a check if you have a metal boat (or similar) and need a portable welding outfit:

Ready Welder II

MOBI-ARC