intermittent charging and fuel issue

I've been chasing this ghost for a few weeks now. 5.7 mag mpi. I've replaced batteries and alternator. Works fine in the drive way and for a while underway until the low voltage alarm starts sounding. I've learned that the pigtail connector has two wires, one(red/yel) going to the starter slave solenoid and then to 50 amp circuit breaker and the other (pur) goes to the EFI harness connector and then to the cannon plug. I was underway and even though the batteries were reading low we were still cruising at 3500rpms fine until it started sputtering from 3500rpms to 0 until cut off. It was then difficult to crank. Once I moved (jiggled) harness on alternator it cranked and we just ran slow back to the dock so the wiring wouldn't short out again. I guess my question is are there any common areas that break down to look for 1st before chasing these wires all over? Has anyone had an issue like this?
Thanks for any advice

Once I moved (jiggled) harness on alternator it cranked and we just ran slow back to the dock so the wiring wouldn't short out again. I guess my question is are there any common areas that break down to look for 1st before chasing these wires all over? Has anyone had an issue like this?

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Ayuh,..... Obviously somewhere 'round the wires you jiggled, 'n it started,.....

I'm guessing here but there could be a break inside one of the wires and you just can't see it. Could also be just that the connection on the alternator has worried loose from vibration and it needs to be nipped up. Look for chafing, insulation cracks, stuff like that. It's likely that you will need to repair the harness with a new bit of wire.

bondo said:

Ayuh,..... Obviously somewhere 'round the wires you jiggled, 'n it started,.....

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Yeah I assumed that. my question was are there any common points of breakdown in those wires? That purple wire travels a long way around the boat in the thick harness. I didn't want to have to cut into the harness and trace wire for days. But thanks for the response. I've ordered a new pigtail with about 10 inch lead of wire. Hoping that fixes it.

Thank you all