Mercury Mariner Service Manual 6, 8, 9.9 210CC Sailpower, Page 24Get this manual
Battery Charging System Troubleshooting A fault in the battery charging system usually will cause the battery to become underchargedCheck battery electrolyte leveland charge batterySee "Electrolyte Level", and "Charging Discharged Battery", precedingIf battery will NOT accept satisfactory charge, replace batteryIf battery accepts satisfactory charge, determine the cause of the charging system problem as follows: Visually check the following1Check for correct battery polarity [red cable to positive (+) battery terminal]If polarity was incorrect, check for damaged rectifierSee "Rectifier Test", following2Check for loose or corroded battery connections3Visually inspect wiring between stator and battery for cuts, chafing; and disconnected, loose, or corroded connections4Excessive electrical load (from too many accessories) will cause battery to run downIf visual inspection determines that battery connections and wiring is OK, perform the following alternator and rectifier tests