The B328 is the biggest dual-role molding in this slice of the B-series: 115 gallons in a 39.5 x 28 x 26 inch block. Twenty-six inches of height is unusual for a marine tank - most of the line crouches under floors - so this one is built for boats with real tankage bays: sailboat keelsons, trawler engine rooms, the deep centerline voids of a displacement hull. If you have the vertical room, you get a footprint under 40 inches long that stores more than anything else on this page.
Dual-role means you decide what it is when you order. With fresh water fittings it is an FDA-compliant potable molding - 115 gallons is genuine passage-making supply. With waste fittings the same shell becomes a high-capacity black or gray holding tank for a vessel that spends weeks between pumpouts. Ronco spin-welds or thread-installs every fitting to your marks in Tustin, California, as they have since 1974. Print the drawing below, plot your ports with the on-page fitting planner, and the blank arrives ready for hose.
Respect the filled weight: about 959 lb of water. That is not a load for tabbed plywood shelves - it needs engineered bearers and proper strapping, and your naval architect or builder should sign off on placement. The tank itself ships at 119 lb, so run the freight cost estimator before checkout. See the rest of the large moldings in boat tanks or the complete family on the Ronco Plastics hub. OneSource Plastics is an authorized Ronco Plastics dealer.
Technical drawing: download the Ronco Plastics B328 dimensional drawing - print it to plan your install and mark exactly where you want fittings located; Ronco installs spin-weld or threaded fittings to your marked spec.
