Mercury 40 Service Manual page 128

TIMING, SYNCHRONIZING, & ADJUSTING
NOTE: Keep viewing the tachometer, as the engine rpm may fluctuate during adjustments.
Keep adjusting the idle rpm screw in order to keep the engine speed at approximately 1000
rpm.
8. Rev engine a few times and let engine idle for 15 seconds. Check that the average vacu-
um values remain between cylinders. Readjust if necessary.
9. Stop engine, remove adaptors and reinstall plugs. Refer to Idle Speed Adjustment and
adjust the idle rpm back to specification.
Page 2C-6
Example
If the vacuum reading of Cyl. #4 is 32 cm, then
adjust carburetor screws 3, 2, and 1 to obtain the
listed averaged vacuum values at the other cylin-
ders.
Cyl. #4: (Base ) . . . . . . . . . . . . . . . . . . . . .
Cyl. #3: . . . . . . . . . . . . . . .
Cyl. #2: . . . . . . . . . . . . . . .
Cyl. #1: . . . . . . . . . . . . . . .
Cyl. Cyl. Cyl.
# 1 #. 2 # 3
= 32 cm
32 cm – 1 cm = 31 cm
32 cm – 2 cm = 30 cm
32 cm – 3 cm = 29 cm
34 cm
32 cm
30 cm
28 cm
26 cm
Cyl.
# 4
90-828631R3 MARCH 1999