Honda BF15D BF20D Outboard Motors Shop Manual., Page 58Get this manual
3) Remove the five 10 mm screws and left engine under cover w"4) Remove the spark plug caps, then remove the spark
UNDER COVER
plugs using spark plug wrench5) Visually inspect the spark plugDiscard the plug if the insulator is cracked or chipped6) Remove carbon or other deposits with stiff wire brush
SPARK PLUG WRENCH
7) Measure the plug gap with wire-type feeler gaugeIf necessary, adjust the gap by bending the side electrode
Standard spark plug
CR5EH-9 (NGK) U16FER9 (DENSO)
Spark plug gap
1 0.80.9 mm (0.0310.036 in) 1