Yamaha F100B F100C Outboards Factory Service Manual, Page 307Get this manual
Ignition system and ignition control system Checking the ignition spark gap
1Remove the cover and disconnect the spark plug caps from the spark plugs2Connect spark plug cap to the special service tool
WARNING
Do not touch any of the connections of the spark gap tester leads Do not let sparks leak out of the removed spark plug caps Keep flammable gas or liquids away, since this test can produce sparks
Checking the high-tension cords
1Remove the high-tension cords from the ignition coil2Measure the high-tension cord resistanceReplace if out of specification