Honda BF50 (5HP) BF5A Outboard Motors Shop Manual., Page 36Get this manual
bINSPECTION
IGNITION COIL
Primary coil Measure the resistance between the wire terminal and the core
PRIMARY COIL RESISTANCE
Secondary coil
Remove the spark plug cap from the spark plug lead and measure the resistance between the core and the spark plug lead
SECONDARY COIL RESISTANCE
6.3-7.7 kS2