1978 Johnson 55 HP Outboards Service Manual, Page 42Get this manual
bAdjust the air gap of the spark tester to 12 inch (12 mm) and connect the tester leads to the high tension leadsSecure the other end of the spark tester to clean engine groundSee Figure 4-14 1Four wire connector 2Three wire connector
Figure 4-15Cable Connectors
Figure 4-14Spark Tester
&,SAFETY WARNING
To avoid possible shock hazards, do not handle ignition coil or tester leads during this testdCrank engine by using emergency starter rope and observe the results at the spark testereIf spark jumps at both gaps, the problem is key switch circuitRefer to key switch testIf there is no spark, or spark at only one gap, remove the jumper wiresNOTE Carefully align the connector halves during assembly to insure proper terminal contactfReconnect the three wire connector and continue troubleshooting procedure
To prevent possible arcing of high voltage, position the tester leads at least inches (50 mm) from any metal surface