2007-2009 Yamaha F15/F20 Outboard Service Manual, Page 95Get this manual
Power unit NOTE: Before installing the timing belt, make sure that the marks on the drive sprocket and driven sprocket are aligned with the marks on the cylinder block and cylinder head9Turn the drive sprocket clockwise turns, and then check that the alignment marks and are aligned
7Remove the timing belt from the driven sprocket, and then remove it from the drive sprocket6 -4 AH 62 41 -XX
S6AG5101
CAUTION:
Do not turn the drive sprocket or driven sprocket when the timing belt is not installedOtherwise the pistons and valves will collide with each other and be damaged8Install new timing belt onto the drive sprocket, and then install it onto the driven sprocket with its part number in the upright position eS6AG5100