1991 Yamaha Outboard Factory Service Manual 9.9 and 15 HP, Page 107Get this manual

1991 Yamaha Outboard Factory Service Manual 9.9 and 15 HP, Page 107

Measure the resistance of the ignition coil and, if either primary coil or the secondary coil resistance is far off specification, replace the ignition coil If the resistance measured is slightly off specification, install the ignition coil onto the engine and check spark strength
2By turning the "GAPADJ" knob, set the spark gap to mm (0.31 in)
Ignition spark gap test WARNING: Be careful not to touch the ignition coil and its vicinity while performing testsAn electric shock may cause injuryNOTE:

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