1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 246Get this manual
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(9.5mm) diameter tilt pin or two 38 in(9.5mm) hardened bolts and nuts thru the transom brackets and swivel bracket in the hole shown
11Run trim "UP"The minimum pressure should be 1300 P.S.I(91 kgcm2)12Run trim "DOWN" to release pressure and remove spare tilt pin or bolts and nuts13Tilt outboard full "UP" and engage tilt lock lever14Slowly remove "Fill" plug to bleed pressure15Open Manual Release Valve to turns to bleed any remaining pressure16Remove test gauge hose and adapter, and install allen plug