1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 121Get this manual
Filling Oil Tank 1Quicksilver 2-Cycle Outboard Oil is recommended for this oil injection systemIn an emergency, when Quicksilver 2-Cycle Outboard Oil is not available, substitute high quality 2-cycle oil that is intended for outboard use and meets BIA rating TC-WII or TC-W3, shown on oil containerBIA rating TC-W is the Boating Industry Association's designation for approved, 2-cycle watercooled outboard oils2Remove fill cap from the oil tank and fill tank with oilRetighten the fill cap