Mercury - Quicksilver Lower Unit Drain and Fill Screw Seal Gearcase Component Nylon and Rubber Composite 19183Q02. Overview. Keeping water out of your lower unit is one of the easiest - and most important - parts of drive maintenance. The Mercury Marine 19183Q02 Quicksilver Drain and Fill Screw Seals provide a tight, reliable seal every time you service your gear lube. Designed to fit 3/8-16 drain and fill screws found on MerCruiser sterndrives and most Mercury and Mariner outboards, these OEM g