I've got an old outboard that uses a Capacitor Discharge Ignition (CDI.) Within the passed month, I've wrecked three of them-- the original, a new one, and another replacement. I've attached the schematic for the outboard. The CDI is labeled as "Switch box."
The wiring harness are over 30 years old, insulation is cracked, and connections look bad. The new CDI states that voltage over +16V could ruin the part. The last CDI broke when I accidentally bumped into the wiring harness.

Can someone either support or refute my thought-- there's either a bad connection or occasional short causing a spike in voltage or amperage at the CDI positive terminal.

I'm almost convinced, but I'd like to get a better understanding. Without knowing a lot about electronics, my thought is that if there's electricity flowing from the battery and from the stator, and I suddenly disconnect the negative, the momentum so-to-speak causes a build up of electricity. Any comments?

(New wiring harnesses and a new CDI will cost $600, so I'd like to know for sure that it won't break again after I replace the harnesses.)

 

There is a reality where any time you disconnect an inductor, the magnetic field that was already established by the flowing current tends to keep the current flowing in the same direction it was already going. If you disconnect in a magic instant, stopping the current instantly, the energy stored in the magnetic field will convert to voltage. That voltage can easily be thousands of volts, and it will pierce any semiconductor you can buy.

There are two ways to avoid this. Either don't do instant switching or give the stored energy a place to go. Automotive electronics must be designed to dissipate inductive voltage spikes. If they weren't, several million cars would stop by the side of the road every day. I wonder why your electronic box doesn't protect itself.

You present a theory. It has something to do with a stator. Now we consider the idea that a voltage generator is running during the disconnect, and you disconnected its ground connection. It seems obvious that a generator which can't tell where ground is will run wild.

I think I just answered your question.