1996 Johnson/Evinrude Outboards 8 thru 15 Four-Stroke Service Manual, Page 263Get this manual
Tachometer Circuit TestsAll Models
INote Verify that all engine and boat wiring and connectors are in
good condition [}] 112-amp systemDisconnect the purple lead between engine wiring harness and rectifierregulatorSet peak-reading voltmeter to "POS" and "50"Connect the meter red lead to engine harness purple lead and meter black lead to clean engine groundWith the engine not running and the key switch in the "ON" position, voltmeter must show battery voltage If the voltmeter shows battery voltage, reconnect the purple leads and go to Step If the voltmeter shows less than battery voltage, check the engine and boat purple circuit
212-amp systemDisconnect the gray lead between the engine wiring harness and rectifierregulatorConnect the meter red lead to rectifierregulator gray lead and meter black lead to clean engine groundWith the engine not running and key switch in the "ON" position, voltmeter must not show voltage If the voltmeter does not show voltage, go to Step If the voltmeter shows voltage, replace the rectifier regulator