Mercury Mariner 25HP 4-Stroke Outboard Service Manual 1997, Page 256Get this manual
Draining and Inspecting Gear Lubricant If gear housing is installed on outboard, disconnect (and isolate) spark plug leads from spark plugs before working near the propeller1With gear housing in normal running position, place clean pan under housing and remove vent plug and fil Vdrain plug (with gaskets)
Propeller Removal
If gear housing is not removed from outboard, before attempting to remove or install the propeller, remove (and isolate) spark plug leads from spark plugs to prevent outboard from starting1Bend tabs of tab washer away from nut[p
a Tab Washer