Yamaha F75F - Page 249

Shimming
8-25
• The resistance of the spring increases the
force required to turn the drive shaft. There
-
fore, to obtain correct measurements, con-
sider the spring resistance force when
turning th
e drive shaft.
• Do
not turn the drive shaft using too much
force. Otherwise, the forward gear will turn,
leading to incorrect measurements.
• A
knocking sound may be heard when the
drive shaft is rotated, but this is the sound of
the pinion contacting the reverse gear and
does not affect the backlash measurement.
k. Turn the drive shaft 180 clockwise,
and then measure the backlash again.
• Measure the backlash at 4 points: “a”, “b”, “c”,
and “d”, turning the drive shaft 180 clock
-
wise after each measurement.
• Write down
the measurement data in the
shimming check sheet.
l. Determine the backlash average, and
then round down the average to 2 dec-
imal places.
Example:
(mm)
m. Check that the forward gear backlash
average is within specification.
Adjust the shim thicknesses if the forward gear
backlash is out of specification.
n. Remove the special service tools from
the propeller shaft.
o. Apply a load to the reverse gear by in-
stalling the propeller “1”, spacer “2”,
and washer “3” (without installing
the
spacer “4”).
p. Tighten the propeller nut “5” to the
specified torque.
q. Repeat steps (j)–(l) to measure the re-
verse gear backlash.
a
b
d
c
Measurement point “a” 0.30
Measurement point “b” 0.36
Measurement point “c” 0.34
Measurement point “d” 0.33
Average 0.3325
Round-down average 0.33
Propeller nut “5” (shimming)
10 N·m (1.0 kgf·m, 7.4 lb·ft)
1
2
4
5
3
T
R
.
.