The 58E features this builder’s proprietary Marlow Captive Sump fuel tank, which is shaped like the vessel’s deadrise and located on the longitudinal center of balance (LCB) so it doesn’t affect trim or cause pitching like a tank located forward of or abaft the LCB. If a 1,500-gallon tank is located 8 feet abaft LCB, it would generate more than 87,000 pounds of pitching moment.
Not only does this tank have a centerline sump that holds about 90 gallons, but also the slope of its sides, combined with Z-shaped baffles, causes significant “flushing” of sediment. With a minimum corner radius of 2 inches, there are no recesses to trap fuel crud or algae that can break loose on a rough day to clog the fuel filters. A fuel pickup for the main engines is at the bottom of the sump, while the generator pickups are staggered so they will run out of fuel sequentially before the mains. The fuel returns from the engines are at the top of the tank, so fuel is cooled before it reaches the pickup point. The fiberglass tanks, which have ABS, BV, ABYC and Germanischer Lloyd approvals, are fireproof and coated with a smooth finish designed for fuel systems. Aside from the innovative design, a desirable feature of the Marlow tank is a man-size port in the top, allowing a worker to enter the emptied tank and polish the interior to keep it spotless.