2005 Yamaha F90TR 90HP Outboards Factory Service Manual, Page 81Get this manual
Power unit 13Install the spring A
10Install new timing belt onto the drive sprocket with its part number in the upright position, and then install the belt onto the driven sprockets by turning it counterclockwise
6 7F-4 241 -00
S6D85260
S6D85290
14Take up the timing belt slack by turning the drive sprocket clockwise at least two full turns15Tighten the timing belt tensioner bolt to the specified torqueTiming belt tensioner bolt: 39 Nm (3.9 kgfm, 28.8 ftlb)