Yamaha Outboard Motors Factory Service Manual F6 and F8, Page 130Get this manual

LOWER UNIT LOWER UNIT CHECKING THE GEAR OIL LEVEL
Check: Gear oil level Level is low Add gear oil to the proper level

CHANGING AND CHECKING THE GEAR OIL LEVEL

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