1990 Johnson Evinrude "ES" 9.9 thru 30 Service Manual, P/N 507871, Page 310Get this manual
Key Switch
1Install the cutoff switch cap and lanyard2Use continuity light or ohmmeter calibrated on high ohms scale to test continuity3Turn the key to the OFF position]
4Connect meter as shown Meter must show continuity5Turn the key to the ON position Meter must show no continuity6With meter connected as shown, push key in while in the ON and START positions Meter must show continuity Meter must show no continuity when key is released