My thoughts Dave, are that the high frequency certainly has the potential to damage nearby sensitive electronics. It can induce currents in things that are "nearby", even if they are not in direct electrical connection with the welding circuit.

The best protection when welding nearby any sensitive electronics, if they cannot be completely removed from the vicinity (often not practical), is to use as little high frequency as you can.

You can do this by using a modern inverter with a good clean ground connection, and an "easy starting" electrode (like a pretty well prepared lanthanated/ceriated/thoriated, of appropriate diameter and adequately "sharp" tip prep), which IME will really reduce the high frequency starting to the point where it is not even perceptible. If I have a problem with arc starting, I can often tell because my garage door starts acting up (light blinking and needs power to be reset before start working normally.) That's a good example of how HF can induce currents in electronics that may be a *few feet* away from where I'm actually trying to weld. When I have good arc starts, never had a problem with any nearby electronics acting up.

Even better would be a "lift arc" starting technique (a feature my machine doesn't have, but I am aware of on other TIG machines.) Such mode of operation is basically *guaranteed* to not use high frequency at all. If I were doing a lot of welding near sensitive electronics, I'd probably look for a machine with that feature.

A transformer style of TIG welding machine, operating in AC mode on the other hand would be a poorer choice for welding near sensitive electronics IMO, as such machines need *continuous* high frequency operation (in order to maintain a stable low-amp A/C arc.)

The main/high welding current, since is only done on no more than 15-30 volts (or something rather), is just not high enough to induce damaging currents in any nearby electrical components that are not either 1. burned from heat or 2. have any of the main welding current actually conducting through them. You can reduce risk of #1 by thinking a bit about where heat you will be generating is going to be transferred, and controlling/mitigating if needbe. You can reduce risk of #2 by being aware of where you hook you your ground clamp so the current stays away from any sensitive electronic componts (IE: hook a clean ground clamp directly to a cleaned metal surface that is part of the metal piece you are welding (the fewer bolted joints you need to travel through, the better because such connections can have resistance.) The worst case scenario for #2 factor above is if you forget to hook you your ground clamp up to your work at all. Don't forget to do that and try to do it securely (so can't bump off.)

In the case of an outboard motor like this, you can see I took some effort to get a good ground, that didn't need to transfer from one bolted part to another to complete the welding circuit. I also figure if the motor does have any sensitive electronics, it's likely they were at the opposite end of the motor. And I figure it's most likely it doesn't have any sensitive electronics (I'm picturing a simple carburetor and magneto ignition system under that cover.)

Maybe others will have some other ideas to add, but those are just my thoughts on the topic.