1991 Yamaha Outboard Factory Service Manual 9.9 and 15 HP, Page 106Get this manual
Spark plug cap replacement 1Remove the spark plug cap from the high-tension cord2Straighten the bent end of the spring and remove the spring3Cut the high tension cord insulator about mm from its end to expose the inner wires
Apply thin coat of grease to the spring and fit the high tension cord into the spark plug cap
Direct current resistance test
Use the pocket tester to determine the resistance and continuity of the primary and secondary coil windings,
When perform ing the secondary leads resistance test, disconnect the spark plug capPrimary coil test