Mercury 15 EFI FourStroke, Service Manual

Page: 312 / 406

1. Position a clean drain pan under the gear housing and remove the fill and vent screws from the gear housing.
a - Vent screw
b - Fill screw
2. Inspect the gear lubricant for metal particles. Presence of a small amount of fine metal particles resembling powder
indicates normal wear. Presence of larger particles or a large quantity of fine particles indicates a need for gear housing
disassembly and component inspection.
3. Note the color of the gear lubricant. White or cream color indicates the presence of water in the lubricant. Check the drain
pan for water separation from lubricant. Presence of water in the gear lubricant indicates the need for disassembly and
inspection of 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 the 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 that is stabilized will be a clear yellow brown in color.
Gear Housing Removal
!
WARNING
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 - Cotter pin
b - Propeller nut
2. Remove the propeller nut, flat washer, propeller, and front thrust washer from the propeller shaft.
3. Turn the coupler to separate the upper and lower shift shafts.
a
b
62824
a
b
6523
Gear Housing (2.15:1)
90-8M0125265 eng NOVEMBER 2017 © 2018 Mercury Marine Page 6A-11