Honda BF9.9A-BF15A Outboard Motors Shop Manual., Page 32Get this manual
SPARK PLUGS 1) Remove the engine cover and spark plug caps2) Use the wrench supplied in the tool kit to remove the spark plugs3) Visually inspect the spark plugsDiscard them if the insulator is cracked or chipped
4) Measure the plug gap with feeler gaugeThe gap should be 0.6-0.7 mm (0.024-0.028 in)Correct as neiessary by bending the side electrode5Check that the spark plug washer in good condition, and thread the spark plug in by hand to prevent cross threading
[I] SIDE ELECTROYE
Standard spark plug
Xl6FSR-U (ND) BF15A: DR-6HS (NGK)
Spark plug gap
mm (0.024-0.028 in)