1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 250Get this manual
Hydraulic Repair TRIM ROD REMOVAL AND REPAIR
5Install trim rod removal tool and pull trim rod from cylinder
NOTE: Power Trim does not have to be removed from outboard to remove trim rods1Tilt outboard to full "UP" position and engage tilt lock lever2Slowly remove "Fill" plug to bleed reservoir pressure3Turn Manual Release Valve to turns (counterclockwise) to bleed remaining pressure4Remove trim rod cylinder caps
NOTE: Place clean pan under trim system to catch fluid
27933Trim Rod Removal Tool (91-44486A1)
CLEANING AND INSPECTIONTRIM RODS AND CAPS
CAUTIONDo not remove check valve (a)Check valve is preset to operate at specific pressureRemoval and installation of check valve could result in improper operating pressure and possible system damage