1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 8Get this manual
Cowl Removal Pull outward on starboard side of front shield (a)Remove spring (b) from latch and open cowls
Filling Oil Injection System
Open starboard cowl (refer to cowl removal on this page)Some earlier outboards will have cowl bracket to hold cowl open as shownFill tank with recommended oil