if have an intermittent alarm going off because the output voltage is exceeding the high voltage allowed, which is as high as 17-18 volts. Sometimes the alarm it will spike up within a few minutes of starting, sometimes within 20 minutes. On the gauge you can see the output voltage creep up from normal quite quickly until it sounds the alarm, but then it seems to settle down and the alarm may or may not sound again, either for this boat ride or next time out. Is this symptom of a bad rectifier as it's been suggested to me? suggestions please would be greatly appreciated