Seventy-five gallons puts the BOAT61W in genuine passagemaker territory - the water budget for a crew, not a couple. Ronco molds it at 54 x 22 x 16 inches, a long deep block, and the maker's sheet lists the bare molding at 48 lb, which tells you how much polyethylene is in this wall. Heavy-duty is not a label here; it is mass you can weigh.
The resin is FDA-compliant and rated for potable water, and the tank comes out of Ronco's Tustin, California plant, rotomolding since 1974. Fittings are installed per order - spin-welded or thread-mounted at the exact locations you mark. Print the drawing below and work through the on-page fitting planner carefully: on a tank this size you are placing fill, vent, pickup, and sender across a 54-inch span, and getting them right the first time matters.
The controlling number is about 626 lb of water when full. That is furniture-scale load; frame the bearing surface, through-bolt the hold-downs, and keep the mass low in the hull. See what sits above and below this capacity in boat tanks, price the shipment on the freight cost estimator, or survey the line at the Ronco Plastics hub. OneSource Plastics is an authorized Ronco Plastics dealer.