Mercury 40 Service Manual page 127

NOTE: Keep engine speed set at approximately 1000 rpm in neutral while synchronizing
carburetors.
a
a -
4. Read the vacuum of cylinder #4. It's not important to be at any specific vacuum setting.
a
1 2 3 4
a -
5. Adjust cylinder # 3 vacuum (turn screw 3) to read one cm less vacuum than cylinder #4.
6. Adjust cylinder #2 vacuum (turn screw 2) to read two cm less vacuum than cylinder #4.
7. Adjust cylinder #1 vacuum (turn screw 1) to read three cm less vacuum than cylinder
#4.
90-828631R3 MARCH 1999
Idle rpm Screw
Vacuum Reading Cylinder #4. – Note, that it's not Important to be at any Spe-
cific Vacuum Setting
TIMING, SYNCHRONIZING, & ADJUSTING
1
2
3
Page 2C-5