Timing; Idle Timing Adjustment; Maximum Timing Adjustment - Mercury 40 Service Manual

Timing

CAUTION
Engine may be timed while cranking engine with
starter motor. To prevent engine from starting
when being cranked, all spark plugs must be re-
moved.
1. Insert Spark Gap Tool (91-63998A1) into each
spark plug boot and attach alligator clips to good
engine ground.
2. Disconnect remote fuel line from engine.
3. Connect remote control electric harness to en-
gine wiring harness.
4. Remove throttle cable barrel from barrel retainer.

Idle Timing Adjustment

5. Connect timing light to No. 1 (TOP) spark plug
lead.
WARNING
While cranking engine, keep clear of propeller as
it may rotate.
6. Shift engine to neutral.
IMPORTANT: To time engine at cranking speed, a
fully charged battery must be used.
7. Hold throttle arm at idle position as shown below,
crank engine with starter motor and adjust idle
timing screw to align T.D.C. timing mark of fly-
wheel with timing pointer. Tighten locknut.
NOTE: Timing will be T.D.C. 2 after adjusting idle
RPM.
55039
TDC
10 0 10
a - Idle Timing Screw
b - Locknut
2C-2 - ELECTRICAL
a
b

Maximum Timing Adjustment

1. Hold control arm so that maximum spark ad-
vance screw is against stop. Crank engine with
starter motor and adjust maximum spark ad-
vance screw to align the specified BTDC timing
mark on flywheel with timing pointer. Tighten
locknut.
c
a - Control Arm
b - Spark Advance Screw
c - Locknut
NOTE: All timing adjustments made to engine under
cranking speed conditions should be verified with en-
gine running and adjustments made if necessary.
This is due to advance characteristics of individual ig-
nition systems.
b
a
51045
90-852572R1 JANUARY 1998