2007-2009 Yamaha F15/F20 Outboard Service Manual, Page 123Get this manual
Power unit
6Align the "1mark on the driven sprocket with the" mark on the cylinder head
CAUTION:
Do not twist, turn inside out, or bend the timing belt beyond the maximum limit of 25 mm (1.0 in), otherwise it can be damaged Do not get oil or grease on the timing belt9Turn the drive sprocket clockwise turns, and then check that the alignment marks and are alignedS6AG5H81
7Align the mark on the drive sprocket with the mark on the cylinder block by turning the crankshaft counterclockwise approximately 90 graduallyS6AG5102