1997+ Mercury 35/40HP 2 Cylinder Outboards Service Manual PN 90-826148R2, Page 81Get this manual
Battery Charging System (14 or 18 Ampere Alternator) Description
The battery charging system components are the stator, voltage regulator and batteryAlternating current (generated in stator alternator coils) flows to the voltage regulator, which changes the alternating current to direct current for charging the batteryELECTRIC START MODELS
Battery Charging System Troubleshooting
A fault in the battery charging system usually will cause the battery to become underchargedCheck battery electrolyte level, and charge batterySee "Electrolyte Level", and "Charging Discharged Battery"If battery will NOT accept satisfactory charge, replace batteryIf battery accepts satisfactory charge, determine the cause of the charging system problem as follows1Check for correct battery polarity [RED cable to POSITIVE (+) battery terminal]If polarity was incorrect, check for damaged rectifierSee "RECTIFIER TEST"2Check for loose or corroded battery connections3Visually inspect wiring between stator and battery for cuts, chafing; and disconnected, loose or corroded connection