Mercury Mariner 30/40 4-Stroke Outboard Service Manual 1998, Page 70Get this manual
IGNITION
ACAUTION
To protect against meter andor component damage, observe the following precautions: 400 VOC test position (or higher) MUST BE used for all testsINSURE th Positive (+) leadterminal of OVA is con nected to the Positive (+) receptacle of meter DO NOT CHANGE meter selector switch position while engine is running andor being "cranked"ALL COM PONENTS MUST BE GROUNDED during testsRunning or "cranking" engine with COl or Ignition Coils ungrounded may damage components
If using meter with built-in OVA, the OVA400 or OVASaO VOC 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 beingcrankedwith all harnesses connected