Yamaha 115-225 HP Outboards Service Manual, Page 73Get this manual
_ D350000
SPARK PLUG 1Check the electrode condition and state of wear, note the insulator colour and the electrode gap2Clean the spark plug with spark-plug cleaner if necessaryUse wire gauge to adjust the plug gap to specification3If the electrode becomes too wornreplace the spark plug4When installing the spark plug, clean the gasket surface, wipe off any grime there may be on the surface of the spark plug, and screw in the spark plug to the correct torque