hello Im trying to ride my jet ski but the battery keeps dieing I tested my rectifier and it is getting no current at all but my stator is kicking out power so could I use a transformer to change the current from AC to DC or 20v AC to 13.5 volts DC
No. Transformers and rectifiers are completely different things. A transformer converts high voltage AC current to low voltage AC and vice versa. A rectifier converts AC current to DC at the same voltage. In your case, you need 4 new rectifiers to convert 20V AC from the alternator to 20V DC and a voltage regulator to fix the output voltage to around 13.5V DC
