1989 Johnson Evinrude "CE" 9.9 thru 30 Service Manual, P/N 507754, Page 303Get this manual
Rectifier Ohmmeter Tests
INote Disconnect
battery cables before proceeding with this
1Disconnect all rectifier leads from terminal board
2Calibrate ohmmeter on high ohmms scale and connect one lead to clean engine ground Connect the other lead to the rectifier yellow gray leadNote the readingReverse the ohmmeter connections or press thereverse polarity" button and note the reading very high reading in one direction and low reading in the other direction indicates that diode is OK Two high readings or two low readings indicate that diode is damaged]]
3Repeat step using the rectifier yellow lead Result should be similar4 Repeat step using the rectifier yellow blue lead Results should be similar