Season 4 begins with Cowboy asking Eugene and Spencer to fortify his compound in preparation for the end days. Included: The guys construct a wood still to make sure that their neighbor will have fuel no matter what.
Cowboy convinces Eugene and Spencer to embark on an expedition for gold, but they encounter an interloper who threatens to steal their treasure.
Eugene and Spencer decide to build a solar-powered hot water heater out of salvaged pipes and old beer cans, but first they need to construct a chainsaw chopper for their friend who has the supplies they need.
The guys hunt for treasure using a metal detector made by Eugene out of bamboo, wire scraps and a salvaged transistor radio.
The guys rid a friend's home of honeybees and decide to start their own honey-making business.
The guys build a wood kiln out of discarded oil barrels and a huge outdoor rotisserie for cooking chickens.
Eugene and Spencer build a trickle-feed irrigation system using bamboo and some scrap metal in hopes of resolving a water feud that is threatening Cowboy's crops.
The guys transform a herb-drying shed into a guesthouse cabin for Spencer's visiting mother-in-law.
Eugene makes a burl bowl for his mom to replace the one her broke.
Eugene and Spencer build an old-fashioned swinging bridge from scavenged rope and hand-hewn bamboo.
The guys build a monster mower to clear an overgrown field, and with any luck, they hope to find a valuable item Cowboy hid there years ago.
Spencer and Eugene help a notorious old moonshiner come up with a contraption to bring heavy supplies to and from his hidden still.
Eugene and Spencer salvage a rusted-solid Winchester M37 and an antique diesel engine from a barn full of scrap.
Spencer and Eugene set out to build a fish farm using nothing but a roll of plastic tarp and some old hay bales.
The guys help a widow get to her doctor appointment on time, but that means first fixing her car, which needs a tire patch, replacement gasket, temporary fan belt and an alternator.
Spencer and Eugene have two days to forge 15 knives for a collector. The boys construct a water wheel to power a homemade hydro-powered grinder—and to power an electric light. Because if they want to meet that deadline, they must pull an all-nighter.
A hillbilly houseboat is built out of a discarded camping trailer.
Eugene and Spencer need to get heavy sacks of mica down from the mountains, so they decide to build a hand-powered pump trolley out of junkyard scraps to make the job easier.
The guys make several trades, one of which involves trapping a critter, in order to obtain the barn wood they need to make a display case.
Mama Gene steps in a gopher hole and breaks her foot, leaving her homebound on the porch. She's plagued by insects, and missing out on the 4th of July festivities. So the boys build her a flame roasting bug zapper, and a hillbilly ninja rocket wheel.
Part 1 of 2. The guys embark on an adventure to retrieve old steel that was left behind in an abandoned underwater town. But first they have to build a salvage barge from junk for their expedition.
Conclusion. Eugene and Spencer attempt to turn a riding mower engine into an outboard motor strong enough to power a salvage barge, which they plan to use to locate a lost sawmill in an abandoned underwater town, where they hope to retrieve any vintage steel left behind.