1987-1993 Mercury Mariner Outboards 70/75/80/90/100/115HP 3 and 4-cylinder Factory Service Manual, Page 37Get this manual
Standard Stator (Alternator Coils) Amperes Output IMPORTANT: Rectifier must be functioning properly for accurate test results to be obtained1If engine is equipped with voltage regulator, disconnect voltage regulator leads at rectifier; reinstall hex nut on rectifier terminal that has yellow stator lead2Remove red wire from (+) terminal of rectifier3Connect RED (+) ammeter lead to rectifier (+) terminal and BLACK () ammeter lead to red rectifier wire4Run engine at 3000 RPM5Meter should readamperes; if not, replace stator
9With engine running at the indicated RPM's, the ammeter should indicate the following approximate amperes: AMPERES RPM IDLE 1000 10 2000 17 3000 18 10If ammeter indicates approximately 18 amperes at 3000 RPM, this indicates the charging system is functioning properly and the battery is being discharged because the amperage draw on the system is greater than the amperage output of the system11If ammeter reads less than 18 amperes, test the stator; refer to "Stator Ohms Test (Alternator Coils Only)" [18 Ampere Stator], precedingIf stator tests OK, replace voltage regulatorrectifier