1994 Johnson/Evinrude "ER" 9.9 thru 30 outboards Service Manual, Page 313Get this manual
Rectifier Ohmmeter Tests Disconnect battery cables before proceeding with this check
III 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 indicates the diode is damaged