Mercury Mariner Outboard 225 3 Litre Service Manual 1994, Page 200Get this manual
8 Slowly removeplug to bleed pressure Hydraulic Repair
TRIM ROO REMOVAL AND REPAIR Note: Power Trim does not have to be removed from outboard to remove trim rods1iilt outboard to full leverposition and engage tilt lock
Open Manual Release Valve to turns to release any remaining pressure
1ORemove test gauge hose and adapter fittingApply Loctite 271 to allen plug threads and reinstall plug 11Fill Power Trim system and purge system; refer to "FillCheck, and Purge precedingft