1992 Johnson Evinrude "EN" 40 thru 55 Service Manual, P/N 508143, Page 289Get this manual
Rectifier Ohmmeter Tests
INotel Disconnect
battery cables before proceeding with this
iii ,.Disconnect all rectifier leads from the terminal boardf4l 2Calibrate ohmmeter on appropriate scaleConnect one lead to clean engine groundConnect the other lead to the rectifier yellowgray leadNote the readingReverse the ohmmeter connections, or press the "reverse polarity" button, and note the reading high reading in one direction and low reading in the other direction indicates the diode is OK Two high readings or two low readings indicates the diode is damaged