1998+ Mercury Mariner 25HP Bigfoot Service Manual, Page 81Get this manual
IGNITION
CAUTION
Failure to comply with the following items may result in damage to the ignition system1DO NOT reverse battery cable connectionsThe battery negative cable is () ground2DO NOT "spark" battery terminals with battery cable connections to check polarity3DO NOT disconnect battery cables while engine is running4DO NOT crank engine with CDI or Ignition Coils not grounded
CAUTION
To protect against meter andor component damage, observe the following precautions: 400 VDC test position (or higher) MUST BE used for all testsINSURE 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 components