Gear Housing Removal - Mercury 25 EFI Service Manual

1. Position a clean drain pan under the gear housing and remove the fill and vent screws with gaskets from the gear housing.
2. Inspect the gear lubricant for metal particles. Presence of a small amount of fine metal particles resembling powder
indicates normal wear. The presence of larger particles or a large quantity of fine particles indicates the need for gear
housing disassembly and for component inspection.
3. Note the color of gear lubricant. White or cream color indicates the presence of water in lubricant. Check the drain pan for
water separation from the lubricant. The presence of water in the gear lubricant indicates the need for disassembly, and
inspection of the oil seals, seal surfaces, O‑rings and gear housing components. Pressure check the gearcase prior to
disassembly.
NOTE: When draining the gearcase for the first time, lubricant may appear cream colored due to the mixing of assembly
lubricant and gear lubricant. This is not an indication of water intrusion. If, during subsequent draining of gearcase,
lubricant appears cream colored or milky, water may be present. The gearcase should be disassembled and all gaskets,
seals and O‑rings replaced. Inspect all components for water damage.
NOTE: Gear lubricant drained from a recently run gearcase will be a light chocolate brown in color due to agitation/
aeration. Oil which is stabilized will be a clear yellow brown in color.

Gear Housing Removal

Accidental starting can cause serious injury. Before removing or installing the gear housing, disconnect and isolate the spark
plug leads. Disable the ignition system by removing the keys from the ignition (if equipped) and engaging the lanyard stop
switch to prevent the engine from starting.
1. Remove the cotter pin from the propeller nut.
a
90-8M0105568 eng MARCH 2016
a - Fill screw
b - Vent screw
b
a
16911
WARNING
!
a - Cotter pin
b - Propeller nut
b
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© 2016 Mercury Marine
Gear Housing
Page 6A-11