1971 Johnson 125HP outboards Service Manual, Page 92Get this manual
ALTERNATOR CIRCUIT CHECKS
Where To Look Cause What To Do UNDERCHARGED BATTERY BATTERY
1Defective battery or worn out battery 2Low electrolyte level 3Corroded terminal connections
Check state of charge Add water Clean with wire brush and coat with petrolatum Tighten securely Check total current draw in circuit Troubleshoot (See page 7-14) Test with ohmmeter Clean and tighten connections Check leads for defective lead insulation or connectorsStator leads are yellowCheck for worn through insulation and check diodes Disconnect rectifier leads and check each diode on HI ohms scale High reading on one check and no reading on another, diodes OK Zero reading both checks, shorted diode Infinite reading both checks, open diode