Yamaha F100B F100C Outboards Factory Service Manual, Page 110Get this manual
Power unit
NOTE: Use deep socket (M46) for this procedure Do not turn the camshaft when loosening the drive sprocket nutCrankshaft holder 20 3: 90890-06552 3Disconnect the cooling water hose 44Remove the bracket 5, spring 6, tensioner 7, and timing belt from the driven sprocket side
Removing the timing belt and sprockets
1Set the cylinder #1 piston position to TDC of the compression stroke by aligning" marks and on the driven sprockets, and the hole on the retaining plate with the notch on the cylinder block