1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 36Get this manual
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", following2Check for loose or corroded battery connections3Visually inspect wiring between stator and battery for cuts, chafing; and disconnected, loose or corroded connection4Excessive electrical load (from too many accessories) will cause battery to run downIf visual inspection determines that battery connections and wiring are OK, perform the following stator and rectifier tests
2Use an ohmmeter and perform the following testIMPORTANT: If stator is mounted on engine, black stator lead (if provided) must be grounded to powerhead when testing3Replace stator if readings are outside ranges shownTest Leads AMPERE STATOR Between YELLOW stator leads Between either YELLOW stator lead and engine ground 16 AMPERE STATOR Between YELLOW stator leads Between either YELLOW stator lead and engine ground 24 AMPERE STATOR Between YELLOW stator leads Between either YELLOW stator lead and engine ground .6 1.1 No Continuity .6 1.1 (R 1) No Continuity (R 1000) .17 .19 (R 1) No Continuity (R 1000) .05 .15 (R 1) No Continuity (R 1000) Resistance (Ohms) Scale Reading (x )