Mercury Mariner 30/40 4-Stroke Outboard Service Manual 1998, Page 93Get this manual

CHARGINGSTARTING SYSTEM
15 Ampere Stator
1Check battery voltage at battery with engine running2If battery voltage is above 14.5-1 5.0 volts, replace voltage regulatorrectifierCheck condition of battery as overcharging may have damaged battery3If battery voltage is below 14.5 volts, charge battery; refer to "CHARGING DISCHARGED BATIERY"If battery can NOT be satisfacto rily charged, replace battery4If battery accepts satisfactory charge, check battery voltage while cranki ng engine; refer to "CHARGING DI SCHARGED BATIERY"lf cranki ng voltage is not acceptable, replace battery5If cranking voltage is acceptable, disconnect the RED (voltage reg ulator) wire bullet connector from the REDPU wire 6Connect RE (+) ammeter lead to RED wire and th BLACK (-) ammeter lead to the RedPUR wi re7Secure starter wires away from flywheel8With engine running at the indicated RPM'sthe ammeter should indicate the following appropriate amperes:

• ATV
• Jet Ski
• Outboard Motors
• Personal Watercraft
• Snowmobiles
• Stern Drives