1998+ Mercury Mariner 25HP Bigfoot Service Manual, Page 83Get this manual

IGNITION
Ignition Diagnostic Procedures

IMPORTANT: If outboard appears to have an ignition system failure, it is recommended that before beginning in-depth troubleshooting:

• ATV
• Jet Ski
• Outboard Motors
• Personal Watercraft
• Snowmobiles
• Stern Drives