Yamaha F150A Service Manual page 244

5. Turn the crankshaft clockwise 2 full turns,
and then check that the mark "a" in the
drive sprocket and the protrusion "b" on
the cylinder block are aligned. Also,
check that the "I" marks "c" and "d" on the
driven sprockets are aligned.
c
b
a
d
7-19
Timing belt
0
1
2
3
4
5
6
7
8
9
10
A