Mercury Mariner 8/9.9HP 4-Stroke Factory Service Manual, Page 42Get this manual
Ignition Test Procedures Direct Voltage Adapter (DVA) WARNING
DANGER HIGH VOLTAGESHOCK HAZARD! Do not touch ignition components andor metal test probes while engine is running andor being "cranked"STAY CLEAR OF SPARK PLUG LEADSTo assure personal safety, each individual spark plug lead should be grounded to engine
CAUTION
To protect against meter andor component damage, observe the following precautions: 400 VDC test position (or higher) MUST BE used for all tests INSURE the Positive (+) leadterminal of DVA is connected to the Positive (+) receptacle of meter DO NOT CHANGE meter selector switch position while engine is running andor being "cranked" ALL COMPONENTS MUST BE GROUNDED during testsRunning or "cranking" engine with CDI or Ignition Coils ungrounded may damage componentsIf using meter with built-in DVA, the DVA400 VDC test position should be used
WARNING
When testing or servicing the ignition system, high voltage is presentDO NOT TOUCH OR DISCONNECT any ignition parts while engine is running, while key switch is on or while battery cables are connected