Fifty-eight gallons is liveaboard territory - showers, dishes, a week between fills - and the BOAT42W delivers it in a 46.75 x 20.75 x 15.5 inch block proportioned for the cavity under a large berth or a cockpit sole with real depth. Ronco molds several distinct 58-gallon footprints precisely because at this size the tank must fit the boat, not the other way around; this is the long-format version.
It is a heavy-duty molding through and through: the thick H.D. marine wall, FDA-compliant polyethylene rated for potable water, rotomolded in Tustin, California by a shop that has done nothing else since 1974. Fittings are installed per order - spin-welded or threaded to the marks you set. Print the drawing below and lay out your fill, vent, pickup, and gauge sender with the on-page fitting planner before ordering.
Do the structural math first: at 8.34 lb per gallon this tank carries about 484 lb when full. That demands continuous bearing under the bottom and honest hold-downs. Compare the other 58-gallon shapes in boat tanks, price delivery with the freight cost estimator, or start from the Ronco Plastics hub. OneSource Plastics is an authorized Ronco Plastics dealer.