LOWER UNIT
REMOVAL & DISASSEMBLY

Always disconnect the battery cable, before removing
lower unit.
1. Shift to “NEUTRAL” position.
2. Remove bolt and trim tab 1.
3. Remove seven (7) bolts 2 and separate gearcase 3 from
driveshaft housing.
4. Remove clutch rod from clutch shaft (if necessary).
5. Place a drain pan under oil drain plug.
Remove oil drain plug 6 first then oil level plug 5 and
allow gear oil to drain.
Inspect oil for water, contaminates or metal.
Clutch rod
NOTE:
Before gearcase is removed completely, disconnect speedometer
pick up tube 4 from gearcase.

6. Remove cotter pin 7 from propeller nut and remove pro
peller nut 8.
7. Remove washer 9, spacer 0, propeller A, stopper B and
spacer C from propeller shaft.
􀀣
To prevent injury from propeller blades, wear gloves
and place a block of wood between the anti-cavitation
plate and the propeller blade tips to lock the propeller
in place.
9. Keep impeller key 6 for reuse and discard plate gasket.
10. Remove three (3) bolts 1 and shift rod guide housing
assembly 2.

11. Remove two bolts 1 securing propeller shaft bearing
housing to gearcase.
12. Using special tools, draw out propeller shaft bearing
housing.
Remove propeller shaft and bearing housing assembly.
􀁜 09930-30104 : Sliding hammer A
09930-30161 : Propeller shaft remover B
13. Hold pinion nut securely, then fit special tool to the driveshaft
and loosen pinion nut.
􀁜 09921-29410 : Driveshaft holder
14. Remove four bolts 1 securing driveshaft oil seal housing
2, then remove oil seal housing and pinion shim 3.

15. Lift out driveshaft assembly 4.
Remove driveshaft collar 5, washer 6, wave washer 7,
washer (with tab) 8 and washer 9 from driveshaft.

Disassembly of propeller shaft components
1. Slide propeller shaft away from reverse gear 3 and bearing
housing assembly 1.
Account for reverse gear back-up shim 2 and reverse gear
thrust washer 4.

INSPECTION
NOTE:
If excessive ware, cracks, defective or other damage is found
on any component, replace component.
NOTE:
Thoroughly wash all metal components with cleaning solvent
and dry with compressed air.
􀀣
Wear safety grasses when using compressed air.
PROPELLER
• Inspect propeller for bent, chipped or broken blades.
Replace or repair if necessary.
• Inspect propeller bushing splines for wear or other damage.
Replace if necessary.
• Inspect propeller bushing for deterioration or slipping.
Replace if necessary.
GEARCASE
• Inspect gearcase for cracks or other damage.
Replace if necessary.
• Inspect pinion bearing for pitting, rough or other damage.
Replace if necessary.
NOTE:
If removal and replacement are required, see “PINION BEARING”
section on page 9-7.

LOWER UNIT
GEARS
• Inspect forward, reverse and pinion gear teeth and engaging
dogs for excessive wear or other damage.
Replace if necessary.
• Inspect forward gear bearing for pitting, rough or other damage.
Replace if necessary.
PROPELLER SHAFT COMPONENTS
• Inspect horizontal slider and connector pin for excessive wear
or other damage. Replace if necessary.
• Inspect clutch dog shifter for excessive wear, chip or other
damage. Replace if necessary.
• Inspect dog pin for bent or other damage. Replace if necessary.
• Inspect propeller shaft / splines for wear, twist or other damage.
Replace if necessary.
PROPELLER SHAFT BEARING HOUSING
• Inspect housing for cracks or other damage. Replace if necessary.
• Inspect propeller shaft bearings and reverse gear bearing
for pitting, rough or other damage. Replace if necessary.
• Inspect oil seals and O-ring for cuts, nicks or tears.

Replacing propeller shaft oil seal
1. Remove retaining ring 1 and washer 2.
2. Extract oil seals 3 using oil seal remover.
􀁜 09913-50121 : Oil seal remover
􀀃
Do not re-use oil seal once removed.
Always use a new oil seal.
3. Apply Water Resistant Grease to inner circumference of
housing.
4. Using an oil seal installer, drive two oil seals (one at a time)
into housing.
The lipped portion of seal should face towards propeller.
Apply Water Resistant Grease to seal lips.
􀁎 99000-25161 : Water Resistant Grease
5. Install washer and retaining ring.

SHIFT ROD GUIDE HOUSING COMPONENTS
• Inspect shift rod guide housing for cracks or other damage.
Replace if necessary.
• Inspect shifter yoke for excessive wear or other damage.
Replace if necessary.
• Inspect oil seal and O-ring for wear, cuts, nicks or tears.
• Inspect shift rod / splines for excessive wear, twist or other
damage. Replace if necessary.
• Inspect detent ball for wear, rough or other damage. Replace
if necessary.
WATER PUMP AND RELATED ITEMS
• Inspect impeller vanes for cuts, cracks, tears or excessive
wear. Replace if necessary.
• Inspect pump case and under panel for cracks, distortion or
corrosion. Replace if necessary.

DRIVESHAFT OIL SEAL HOUSING
• Inspect housing for cracks or other damage. Replace if necessary.
• Inspect oil seals and O-ring for wear, cuts, nicks or tears.
Replacing driveshaft oil seal
1. Extract oil seals using oil seal remover.
􀁜 09913-50121 : Oil seal remover
2. Apply Water Resistant Grease to inner circumference of
housing.
􀁎 99000-25161 : Water Resistant Grease
3. Using an oil seal installer, drive two oil seals (one at a time)
into housing.
The lipped portion of seal should face towards water pump
case.
Grease inner lips of seal.

1 Dust seal
2 Shift rod guide housing
3 Bolt
4 Ball
5 Spring
6
7 O-ring
8 Washer
9 Circlip
0 E-ring
A Shift rod
B Shifter yoke
C Pin
D Horizontal slider
E Magneto
F Grommet
G Water pump case
H Pin
I Bolt
J Key
K Water pump impeller
L Pump case under panel
M Gasket
N Exhaust seal
O Exhaust seal plate
P Union
Q Hose
R Nipple
S Gearcase
T Bolt
U Bolt
V Pin
W Anode
X Washer
Y Bolt
Z Trim tab
[ Bolt
\ Screw
] Water filter PORT
^ Water filter STBD

WATER PUMP
1. Place dowel pins 1, under panel gasket 2 and under panel
3 into position.
2. Insert key 4 in driveshaft and slide impeller 5 onto
driveshaft, ensuring that key and keyway are aligned.
3. Install pump case 6 while rotating driveshaft clockwise to
flex impeller vanes in correct direction.
4. Tighten four pump case bolts to specified torque.
􀀢 Pump case bolt : 20 N.m (2.0 kg-m, 14.5 lb.-ft.)
PROPELLER INSTALLATION
1. Install spacer 1 and propeller stopper 2 onto propeller
shaft, then slide on propeller 3.
2. Fit spacer 4, washer 5 and nut 6, then tighten nut to
specified torque.
􀀢 Propeller nut : 55 N.m (5.5 kg-m, 40.0 lb.-ft.)
3. Push cotter pin 7 through nut and shaft, then bend to
secure.
LOWER UNIT INSTALLATION
1. Apply clutch rod splines with Water Resistant Grease,
then install clutch rod 1 by aligning clutch rod splines
with splines in clutch shaft.
2. Ensure that shift rod 2 is at neutral position.
NOTE:
Before install lower unit assembly, bring shift to neutral position
by turning shift rod.

3. Insert two dowel pins 3.
4. Apply driveshaft splines and shift rod splines with Water
Resistant Grease.
5. Apply Mercury Silicone Seal lightly to mating surfaces of
gearcase and driveshaft housing.
6. Set clutch control lever 4 at neutral position, then slide
lower unit 5 into place, ensuring that top of driveshaft engages
properly with countershaft and that water tube locates
in water pump case outlet.
NOTE:
In order for shift rod splines and clutch rod splines to be aligned
correctly, clutch rod may need to be turned slightly right or left.
7. Apply Silicone Seal to seven gearcase bolts 6 and tighten
them to specified torque.
􀀢 Gearcase bolt : 55 N . m (5.5 kg-m, 40.0 lb.-ft.)
􀁎 99000-25161 : Water Resistant Grease
􀁍 99000-31120 : Mercury-Mariner Silicone Seal
8. Move clutch control lever 4 to forward and reverse positions
from neutral position to check proper gear engagement.
GEAR OIL
Fill gearcase with specified gear oil.
(See “PERIODIC MAINTENANCE / GEAR OIL” section on page
2-6)
􀁌 99000-22540 : Mercury-Mariner Outboard Motor Gear Oil.