2009 Yamaha F40 Outboard Service Manual, Page 195Get this manual
Power unit 3Remove the drive sprocket nut b, the retaining plate d, the drive sprocket e, and the Woodruff key f
Removing the timing belt and sprocket
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 damaged1Remove the timing belt from the driven sprocket side
2Loosen the drive sprocket nut b
4Loosen the driven sprocket bolt g, and then remove the driven sprocket hNOTICE: Do not turn the camshaft when loosening the driven sprocket bolt