Mercury 35/40HP 2 Cylinder Outboards Service Manual PN 90-42794--1, Page 28Get this manual
Rectifier Test AWARNING
Disconnect battery leads from battery before testing rectifierNOTE: Rectifier can be tested without removing from engine1Disconnect all wires from terminals on rectifier
NOTE: If your test results turn out exactly reversedthe rectifier is good and need not be replaced Reversed results can occur due to VOA meter's internal battery polarityBlack Test Lead Red Test Lead