1991 Yamaha Outboard Factory Service Manual 9.9 and 15 HP, Page 76Get this manual
LOWER UNIT OVERHAUL DESCRIPTION
If disassembly of the lower unit or bracket unit is required, it is necessary to remove the powerhead assembly(Refer to powerhead removal page 4-1
WARNING:
When removing gear case from upper case, shift into neutral and remove the spark plug caps from all the spark plugsOtherwise, the engine may start suddenly, and thus serious injury may result
GEAR CASE REMOVAL It is possible to remove the gear case from the upper case without removing powerhead
Loosen the shift rod lock nutSeparate lower and upper shift rod by moving the shift rod connecting nut upward2Remove the bolts (four) securing the upper casing and gear case, and remove the gear case1Shift rod connecting nut