1991 Yamaha Outboard Factory Service Manual 9.9 and 15 HP, Page 134Get this manual

ENGINE MISFIRES
First check for spark to find cause

Fuel tank Fuel is deteriorated or dirty Fuel filter Clogged Carburetor .Clogged

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