Mercury Mariner 25HP 4-Stroke Outboard Service Manual 1997, Page 153Get this manual
Preparation for Power head Removal Engine could possibly start when turning flywheel during removal and installationTo prevent thi type of accidental engine starting and possible serious injury, always remove spark plug leads from spark plugs1On electric start modelsdisconnect the battery cables from the batteryRemove battery cables from engine2Disconnect the power trim wires (if so equipped)aFuel Pump