1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 287Get this manual
"UP" Pressure Check IMPORTANT: Insure battery is fully charged before performing tests1Tilt outboard to full "Up" position and engage tilt lock lever2Slowly remove "Fill" plug to bleed pressure from reservoir3Turn Manual Release Valve to turns (counterclockwise) to bleed any remaining pressure4Remove allen plug
6Disengage tilt lock lever
CAUTION
Failure to install spare tilt pin (or hardened bolts and nuts) in hole shown could result in transom bracket failure and possible injury7Move outboard "In" until hole in swivel bracket "ear" aligns with the third tilt hole in transom bracketLock engine in trim range by installing 38 in(9.5 mm) diameter tilt pin or two 38 in(9.5 mm) hardened bolts and nuts thru the transom brackets and swivel bracket in the hole shown