2009 Yamaha F40 Outboard Service Manual, Page 196Get this manual
Flywheel magnet and timing belt
Installing the sprocket and timing belt
Do not turn the crankshaft or the driven sprocket when the timing belt is not installedOtherwise, the piston and valves could collide with each other and be damaged1Install the driven sprocket a, and then tighten the driven sprocket bolt to the specified torque
3Tighten the drive sprocket nut to the specified torque