1995 Mariner Mercury Outboards Service Manual 50HP 4-Stroke, Page 26Get this manual
Ignition Test Procedures Direct Voltage Adapter (OVA)
Test procedures and specifications are provided for checking primary ignition voltage while the engine is running andor being "cranked" with all harnesses connected
DANGERHIGH 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
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 connected1
CAUTION
Failure to comply with the following items may result in damage to the ignition systemDO NOT reverse battery cable connectionsThe battery negative cable is (-) ground
2DO NOT "spark" battery terminals with battery cable connections to check polarity3DO NOT disconnect battery cables while engine is running4