Yamaha Marine Outboards F4A/F4 Factory Service Manual, Page 212Get this manual

LOWER UNIT
SERVICE POINTS
Lower unit removal

9It is possible to remove the Lower unit from the upper case without removing the power unit9Set the shift lever to "REVERSE" position, then remove and install the lower unit1
1Remove:

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