1990 Johnson Evinrude "ES" 40 thru 55, P/N 507872, Page 260Get this manual
Power Supply Tests 1Disconnect battery cables from battery[':;l 2Disconnect yellowblue, yellowgray and yellow power supLJ ply leads from the terminal boardr:;') 3Disconnect the yellowred power supply lead from the stator
4Disconnect the warning horn 3-pin Amphenol connectorr:;l 5Calibrate ohmmeter on Rx100 scaleConnect meter black lead to terminal "8," purple lead of engine's warning horn connectorr-, 6Connect meter red lead to power supply yellowred leadmeter readingReverse the ohmmeter connections or press the "Reverse Polarity" button and note the reading