03 Bayliner 195 3.0 alternator sensing wire short

[Mxer1389]

I have a 03 Bayliner 195 runabout with a 3.0 and I have a short that I have narrowed down to the alternator sensing wire. It is shorting to engine ground. If I unplug the ignition(purple)/sensing(red/purple) wires the short goes away. I have replaced the alternator(new not remanufactured) and that didn't help as I thought it maybe the diode internally. I don't know where to go from here. Didn't know if anyone might have any suggestions because I'm out of ideas and I'm new to working on boats. Any help would be appreciated.

 

[alldodge]

Is this a Mec, VP or other?
How do you know it has a short, fuse blowing or other?

 

[Mxer1389]

The sensing wire is producing 12v and when plugged in it shorts the alternator case and then to the engine. I also had an issue with the circuit breaker being corroded and not functioning. I am replacing that today. The whole boat when I got it had a parasitic draw of .5amps. I don't have any fuses blown which is weird just the stuck breaker. I'm not sure what you mean by Mec or Vp though

 

[alldodge]

Merc, VP is the motor a Mercruiser, Volvo Penta or other

The sense wire would be red/purple and if it shorted to the Alt case the wire should get hot and the 50 amp breaker trip. The 50 amp breaker does not trip if its pressed in. Only way it trips is if current exceeds rating

If its the purple wire which energizes the field, and if it went to ground it should blow the ignition 20 amp fuse at the helm

 

[Mxer1389]

Merc, VP is the motor a Mercruiser, Volvo Penta or other

The sense wire would be purple/red and if it shorted to the Alt case the wire should get hot and the 50 amp breaker trip. The 50 amp breaker does not trip if its pressed in. Only way it trips is if current exceeds rating

If its the purple wire which energizes the field, and if it went to ground it should blow the ignition 20 amp fuse at the helm

Merc, VP is the motor a Mercruiser, Volvo Penta or other

The sense wire would be purple/red and if it shorted to the Alt case the wire should get hot and the 50 amp breaker trip. The 50 amp breaker does not trip if its pressed in. Only way it trips is if current exceeds rating

If its the purple wire which energizes the field, and if it went to ground it should blow the ignition 20 amp fuse at the helm

It is a Mercruiser 3.0 I have positive hooked up to the battery and am testing with multimeter from the -battery to the case. I haven't hooked the battery up fully as to not blow anything. Even though it wasn't blowing anything before. I can hook it up when I get home and see if the wire is getting hot, in a couple hours.