Yamaha F100B F100C Outboards Factory Service Manual, Page 322Get this manual
TRBL SHTG
Troubleshooting
NOTE: To diagnose mechanical malfunction, use the troubleshooting charts pertaining to the trouble located in this chapterAlso, when checking and maintaining the outboard motor, see Chapters 8, to check the part necessary to carry out safety maintenance Check that all electrical connections are tight and free from corrosion, and that the battery is fully charged to 12 V
Power unit
Symptom: Engine does not crank Check the starting system Check the power unitCheck that the gearshift is in the neutral position