Ignition Troubleshooting; Ignition Diagnostic Procedures - Mercury 15XD Service Manual

Ignition Troubleshooting

DANGER - HIGH VOLTAGE/SHOCK HAZARD! Do not touch ignition components
and/or metal test probes while engine is running and/or being "cranked". STAY
CLEAR OF SPARK PLUG LEADS. To assure personal safety, each individual
spark plug lead should be grounded to engine.
When testing or servicing the ignition system, high voltage is present. DO NOT
TOUCH OR DISCONNECT any ignition parts while engine is running.

Ignition Diagnostic Procedures

TROUBLESHOOTING TIP: With engine running, use inductive timing light to check spark
advance of each cylinder as throttle is opened and closed. If timing advances and retards
smoothly on each cylinder, ignition system is MOST LIKELY functioning properly
IMPORTANT: If outboard appears to have an ignition system failure, it is recom-
mended that before beginning in-depth troubleshooting:
a. Ensure that the engine is mechanically sound condition. (Fuel System, Cylinder
b. Check all engine ground leads for loose or corroded connections.
c. Disconnect and reconnect ignition harness connectors to verify proper continuity.
PROBLEM
1. No Spark or Weak Spark on Both Cylinders
2. No Spark or Weak Spark on 1 Cylinder
3. Timing Fluctuates -- Note: It is normal for timing
to fluctuate 2° -3°@ Idle.
-- If engine RPM exceeds
5800, switch box will retard
timing from 25°BTDC to 15°
BTDC
-- If engine RPM drops below
600, idle stabilizer in switch
box will advance timing to
as
high as 10°BTDC @ crank
ing speed of 300 RPM.
4. Timing will not Advance -- Note: If timing will not
ing
5. Engine Misfires @ High RPM
90-826883 R2 JUNE 1998
Compression etc.).
advance on only
1 cylinder, check wir-
for shorted trigger wire
WARNING
WARNING
CORRECTION
No Spark -- Trigger, Stator, Ignition Switch Box or
Bad Ground Connection from Switch Box to Block
Weak Spark -- Stator
Ignition Switch Box or Coil
Shorted Trigger Wire or Ignition Switch Box
Defective Switch Box
Defective Coil
Defective Switch Box
IGNITION
Page 2A-13