Yamaha F100B F100C Outboards Factory Service Manual, Page 253Get this manual
Power trim and tilt motor (F100B) 6Measure the brush lengthReplace if out of specification
Assembling the power trim and tilt motor
1Install the oil seal into the motor base as shown
Brush length limit f: 4.8 mm (0.19 in) 7Check the base for cracks or damageReplace if necessary8Check the bearing and oil seal for damage or wearReplace the PTT motor base if necessary2Install the brush holders 3, brushes 4, PTT motor leads 5, and screws to the motor base as shown