1997 Johnson Evinrude "EU" 9.9 thru 30 2-Cylinder Service Manual, P/N 507263, Page 317Get this manual
Rectifier Ohmmeter Tests9.9-30
INote Disconnect
battery cables before proceeding with this
1Disconnect all rectifier leads from terminal board
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 indicate the diode is damaged
3Repeat Step using the rectifier yellow lead Results should be similar4Repeat Step using the rectifier yellowblue lead Results should be similar