1998 Mercury 9.9/15HP 4-stroke outboards factory service manual, Page 61Get this manual
IGNITION
Ignition Diagnostic Procedures
TROUBLESHOOTING TIP: With engine running, use inductive timing light to check spark advance of each cylinder as throttle is opened and closedIf timing advances and retards on each cylinder, ignition system is MOST LIKELY functioning properlyIMPORTANT: If outboard appears to have an ignition system failure, it is recommended that before beginning in-depth troubleshooting: Ensure that the engine is mechanically sound condition(Fuel System, Cylinder Compression etcCheck all engine ground leads for loose or corroded connectionsDisconnect and reconnect ignition harness connectors to verify proper continuity
SUGGESTED TESTING PROCEDURES NOTE: The following recommended tests and probable causes are not listed in any specific orderThe technician should use this table as guide to help isolate and test the specific problemconditionAlways perform the DVA tests first (if applicable), then perform resistance test to validate suspected component failure
Recommended Test
(1) DVA TEST (Direct Voltage Adapter) (2) OHM TEST (Resistance Testing) (3) Replace Component and Retest (4) Mechanical TestRepair PROBLEMCONDITION No Spark Condition (Both Cylinders) Probable Cause Crank Position Sensor Stator (ECM) Stop Circuit Short to Ground:stop circuit leadlanyard stop switchtiller handle stop button (if supplied)remote control harness Ignition Coil Primary Circuit Shorted to Ground Spark Plugs Open Ground Condition:ignition coilstator ground(ECM) High Tension Lead Spark Plug Cap (Resistor) Spark Plug Boat Under Propped Propeller Hub Spun Perform Test No2 1-2 4