1998 Mercury 9.9/15HP 4-stroke outboards factory service manual, Page 59Get this manual
IGNITION
ALL COMPONENTS MUST BE GROUNDED during testsRunning or "cranking" engine with CDI or Ignition Coils ungrounded may damage components
If using meter with built-in DVA, the DVA400 or DVA500 VDC test position should be used
NOTE: Test leads are not supplied with the Direct Voltage AdapterUse test leads supplied with multi meterTest procedures and specifications are provided for checking primary ignition voltage while the engine is running andor being "cranked" with all harnesses connected