So then we agree that there likely was a high resistance, or intermittent contact. At one spot, i.e. in the outlet box, right?
In that case, running everything at at 80% of rated power is not a solution.
Such a sizzle-spot will start a fire at 15 amps, as it did.
Run it at 80%, let it corrode a bit further, and it will start the same fire at 12 amps.
And so on, you can't reduce the load until there is not enough power to start a fire.
The only remedy is getting rid of the (well, all) defective, high resistance, parts and connections. (I think we agree that the wires will corrode at the connection points, right?)
If you notice a problem like this, and just reduce the load on the wiring, you basically are ASKING the fire hazard to come back another time when you are not looking.
Btw, I think sizzle is arcing, not boiling insulation.
I disagree. It isn't always that simple.
The boat is an '85 Catalina. The boat is nearly 30 years old, which offers plenty of time for age and corrosion to introduce extra resistance into an electrical circuit.
My assumption is that the OP is running over 80% of the rating for the circuit, at the end of a long wire run, the wiring or the contacts in the outlet begin to heat up, it melts down, causing the "sizzle" and now the outlet is out of commission.
As I said in my post where you quoted me, running at close to 100% of the circuit's rating continuously, on 30 year old wiring and equipment, is likely to induce extra heat, which would eventually cause a failure.
You make it sound as if electrical components don't at all to break down with age, especially in a marine environment, and that it's safe to run at 100% of a circuit's rating indefinitely. I disagree with that.
The "80% rule" not only applies to vessels, it applies to shore-side installations that aren't even subject to the constant motion and corrosion of the marine environment.
That's cool though. You be you, and I'll be me.