Mercury 90 Service Manual

6A-8 - LOWER UNIT 90-830234R3 DECEMBER 1997
Gear Case Identification
CAUTION
Identify gear case design to ensure correct
components are being installed. Design I - “3 Jaw
Reverse Clutch” (a) gear case identified with
straight machined edge for trim tab screw
mounting surface. Design II - “6 Jaw Reverse
Clutch” (b) gear case identified with angled
machined edge for trim tab screw mounting
surface.
a
b
1987 – 1997 1998 and Newer
“3 Jaw Reverse Clutch” “6 Jaw Reverse Clutch”
a - Design I - “3 Jaw Reverse Clutch” Gear Case Identifier
b - Design II - “6 Jaw Reverse Clutch” Gear Case Identifier
Removal
WARNING
To prevent accidental engine starting, remove
(and isolate) spark plug leads from spark plugs
before removing gear housing.
1. Remove (and isolate) spark plug leads from
spark plugs.
2. Shift engine into forward gear.
3. Tilt engine to full “Up” position.
4. Remove fasteners.
5. Remove locknut and washer.
6. Remove gear housing.
a
b
53992
a - Fasteners (2 each side)
b - Locknut and Washer
Disassembly
Draining and Inspecting Gear
Housing Lubricant
WARNING
If gear housing is installed on engine, to avoid ac-
cidental starting, disconnect (and isolate) spark
plug leads from spark plugs before working near
the propeller.
1. With gear housing in normal running position,
place a clean pan under housing and remove the
two vent screws and one fill/drain screw (with
gaskets).

Mercury 90 Specifications

General

Brand	Mercury
Model	90
Category	Outboard Motor
Language	English