Mercury Mariner Outboard 225 3 Litre Service Manual 1994, Page 50Get this manual
3 Inspect rotor for an open circuitUsing an ohmmeter, check for continuity between slip ringsResistance should not exceed ohmsIf no continuity exists, rotor is defective
STATOR TEST 1With rectifier removeduse an ohmmeter to check for short circuit between each stator lead and the stator frameIf CONTI NUITY exists, stator is defective
aSlip Rings
Check rotor for short to groundNO CONTINU ITY should exist between slip rings and roto shaftIf CONTINUITY exists, rotor is defective