Mercury Mariner Outboards 2.2 / 2.5 / 3.0 Service Shop Manual, Page 11Get this manual
Servicing Spark Plug 1Open access cover on outboard motor2Disconnect spark plug lead and remove spark plug using socket provided in tool kit
IMPORTANT: DO NOT use automotive grease in the gear housing assemblyUse only Quicksilver Gear Lubricant
Servicing Spark Plug (Models 2.5-3.0 shown) IMPORTANT: Use same type of spark plug that is specified on page 1-1Set spark plug gap at .040 in(1mm)
aLubricant Fill PlugLubricant Vent Plug
Gear Housing Lubrication
3Install new spark plug Startthreads one or two turns with fingers to avoid danger of cross-threading4Seat plug finger-tight on gasket; an additional 14turn with wrench generally will be sufficient to tighten Do not overtighten 5Inspect spark plug leadIf insulation is damaged or deteriorated, install new lead 6Connect spark plug lead Reinstall access cover