1998 Johnson Evinrude "EC" 90, 115 SPL Service Manual, P/N 520209, Page 242Get this manual
Rectifier Ohmmeter Tests
INoteDisconnect
battery cables before proceeding with this
check1Disconnect 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 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 damaged3Repeat Step using the rectifier yellow lead Results should be similar