2005 Yamaha F90TR 90HP Outboards Factory Service Manual, Page 79Get this manual
Power unit
Replacing the timing belt
CAUTION:
Do not turn the drive sprocket counterclockwise, otherwise the valve system may be damaged Do not remove the ignition timing pointer Do not turn the drive sprocket or the driven sprockets when the timing belt is not installedOtherwise the piston and valves will interfere with each other and be damaged1Remove the flywheel magnet cover2Loosen the flywheel magnet nutNOTE: Apply force to the crankshaft end until the flywheel magnet comes off the tapered portion of the crankshaft
CAUTION:
To prevent damage to the engine or tools, screw in the puller set bolts evenly and completely so that the puller plate is parallel to the flywheel magnet