We have a 1990 mantra gullwing jet boat with a 454 bbc. When we turn off the ignition the engine continues to run and the electronics (gauges) don't turn off. We tried replacing the ignition, and the wiring seems to be good. It is not the alternator because we disconnected it and it still happens. Any ideas?

You're wired incorrectly somewhere - your switch does nothing but start the engine, right? Somehow your power is bypassing your switch, look under the dash and follow your wires from the switch perhaps you can find where the power is coming from. If that doesn't work pull fuses one at a time until the engine dies, then follow that circuit.

You're wired incorrectly somewhere - your switch does nothing but start the engine, right? Somehow your power is bypassing your switch, look under the dash and follow your wires from the switch perhaps you can find where the power is coming from. If that doesn't work pull fuses one at a time until the engine dies, then follow that circuit.

what he said

NOT AN IGNITION PROBLEM!!

The alternator excitor wire is feeding back juice to the coil wire through the “ign.” terminal on the switch.  You need to install a diode on the excitor wire.  The Radio Shack part number 276-1661 this is a 6A 50V rectifier diode ($2.49/pk of 4). Wire it up with the stripe toward the alternator.

And I unhooked the wires from the alternator and the problem persisted. As for the ignition I will double check and test the wires. Here is a better pic of it. 

As for the two red wires. They are booth hot.

Yes there are 3 purple wires total 2 into the one connector and another separate one with its own connector hiding behind the tape.

Ok. We are going to start going through the wiring now. Thank you for your help. We will try everything you suggested. And I will post on here if we figure it out or not. Thanks again!

One of the purple ignition wires is hot. The one that comes from the harness.

What should we do with it?