Tohatsu 90hp TLDI errors and self-diagnosis functions

I'm beginning to suspect that the ECU has lost its mind (does that happen?). One of the codes I was getting earlier was the #2 ignition coil. I replaced that with a brand new coil (and replaced all 3 spark plugs). But on the last run, I still got the code for the #2 ignition coil. Unlike the fuel injector, there's really no way to screw up the coil replacement. So I don't know what's going on.

By the way, all the while, the engine seems to run fine without audible alarms. I just get these warning lights. Is the engine about to fail? Or is it safe to boat in the short term? In other words, is it more like the check-engine light coming on when it's time to change the oil....the engine will be fine if you keep going in the short/medium term.

Possible to have a flaky ECU, but extremely rare. Most common is a minor, overlooked wiring issue, and of those, the most overlooked are grounds.