Yamaha Outboard Motors Factory Service Manual F6 and F8, Page 246Get this manual
THERMOSTAT, TIMING BELT AND GEARS INSTALLING THE DRIVE GEAR
1Install: Woodruff key Drive gear Washer Lock washer 4
Install the washer as shown in the diagram on the left so that the curvature extends in the upward direction(It is in the reverse direction from the curvature of the flange of the drive gear Pass the tab of the lock washer through the hole in the drive gear and washer2Install: Drive gear nut Crankshaft holder: YB-0656190890-06561