Troubleshooting fuseable link failure
Looks like there was a lot of heat st the the bulkhead connection may that's where the problem is
OK. When you're back there see which ones took the most heat. That will provide more clues to nature of the problem.
Also, here's another good reason to check the circuits for resistance. Measure from P to J. High resistance means bad connections or wires in that circuit (J to ammeter to main splice to P). Infinate resistance means something broke or burned through.
You can check other circuits the same way. For example, P to N should have low resistance (when the start switch is in the run position).
If you haven't done it yet, its probably time to disconnect the bulkhead connectors. At least the one connector with power wires. There's a catch on the top and another on the bottom of each connector. Sometimes it helps to use a thin screwdriver to hold each one open while pulling the connector back. Steady force straight back, but a little wiggling it up and down helps break corrosion and dirt.
Once the connector is off you can get a better measurement of the inside circuits. Also you can better evaluate each terminal within the bulkhead connectors. The male terminals are pretty easy to clean, the females are more difficult. It's not too hard to remove the terminals and clean 'em good if needed.