1991 Yamaha Outboard Factory Service Manual 9.9 and 15 HP, Page 47Get this manual
POWER HEAD OVERHAUL DESCRIPTION
The power head consists of in-line twin cylinders, each with bore and stroke of 56 mm (2.2 in) and 50 mm (2.0 in)The total piston displacement is 246 cc (15.0 in)To produce simultaneous sparks in the two cylinders, capacitor-discharge ignition (COl) system is used
Starting system 1Manual starting system recoil hand starter is used to start the engine2Electric startermanual starting system Both starter motor and manual starter are used to start the engineElectric starter model battery wires 1Remove the battery wires from the main switch and the electric motor
PREPARATION FOR REMOVAL 1All dirt, mud, dust, and foreign material must be cleaned from the engine before the engine is removed and disassembledThis will help keep foreign material out of the engine2Before engine removal and disassembly, be sure that you have the proper tools and cleaning equipmentWith them, you can perform your work cleanly and efficiently