340 DA 7.4 MPI Not charging

[artswarlock]

I get 15v at the alternator but 12v to the battery. I traced the wire on the schematic from the alt to the solenoid then off the same terminal to the isolator Then from there back to the battery. I pulled the wire off the isolator an got 6v and dropping 1 time 12v another. I took the boat out for the first time this weekend and the port engine would only run about 2k rpm after cruising for a while the charge got up to 13v and it picked up a bit more rpm. There seems to be something robbing voltage or a short. The wire bundle is very large and I wondered if anyone had any idea's before i got into it. Thanks

 

[fc3]

Bad isolator. Also, never disconnect the output wire (orange) from the battery when the engine is running. Without a load on the alternator, is is possible that the charging voltage will spike to a voltage greater then the rectifiers peak inverse voltage rating. Then you have to either replace the alternator or tear it down to replace the rectifier assembly.

Sounds like you have a bad isolator. However, on my 1999 330DA, when Sea Ray installed the isolator, they cut the orange charging wire and spliced in a new wire that ran to the isolator and then from the isolator back to the wiring harness. One of the crimps was bad and making intermittent contact.

Best regards,
Frank

 

[artswarlock]

Frank, I think you may have hit the nail on the head. I saw the crimp connector and I will check them before buying a new isolater. And I think I will pull the alternator and have it checked at the shop. One timne I saw a very high spike in voltage at first thought it was my meter but no load makes sense. Thanks so much for your help , it will sure make my life a whole lot easier with your direction. Thanks Art