Checking And Adjusting Forward Gear Backlash - Mercury 25 EFI Service Manual

7. Pull up on the driveshaft and insert the thickest feeler gauge that fits snugly between one tooth of the pinion gear and the
high point of the Pinion Height Tool.
l
Description
Water pump cover screws
Pinion Height Tool
8. Rotate the driveshaft 120 degrees in a clockwise direction and take another reading.
9. Repeat this process until three readings have been taken.
10. Add the three readings together and divide the sum by three to get the average pinion height.
Pinion Height
Average pinion height
11. If the average pinion height is not correct, remove the water pump cover and base. Add to or subtract from the shims
located on top of the upper driveshaft bearing to obtain the proper average pinion gear height. Reinstall the pump cover
and base. Torque the pump cover screws to specification. While pulling up on the driveshaft, repeat the measurement
process at three different locations 120 degrees apart.
12. After the correct pinion gear height is achieved, remove the pinion nut, pinion gear, water pump cover, and water pump
base.

Checking and Adjusting Forward Gear Backlash

NOTE: Forward gear shims are located between the forward gear and the forward gear bearing. Adding shims reduces
backlash, removing shims increases backlash.
1. Lift the driveshaft assembly enough to install the forward gear bearing assembly into the forward gear race.
2. Secure the pinion gear to the driveshaft with the pinion nut. Torque the nut to specification.
3. Install the water pump cover and water pump base onto the gearcase. Secure the pump cover and base with the pump
cover screws. Torque the screws to specification.
4. Install the forward gear Backlash Preload Tool into the gearcase.
5. Use a screwdriver to turn the tool shaft to apply light pressure against the forward gear assembly to prevent forward gear
rotation.
90-8M0105568 eng MARCH 2016
c
f
m
k
a
a - Driveshaft (pull up)
b - Water pump cover
c - Water pump cover screws
b
d - Water pump base
e - Shims
d
f - Upper driveshaft bearing
e
g - Oil slinger
h - Pinion gear
i - Flat side of Pinion Height Tool faces up
j - Forward gear bearing race
g
k - Measure between bottom of pinion tooth and high
point of tool
h
l - Pinion Height Tool
m - Feeler gauge
i
j
17368
0.60–0.64 mm (0.023–0.025 in.)
© 2016 Mercury Marine
Nm lb. in.
6 53
91‑895218
Gear Housing
lb. ft.
Page 6A-35