I hope this works linking three quotes.
Now I am not trawler, strictly a coastal cruiser, gas not diesel.
But I have older GM 350 (5.7) based carburated engines. The only electronics is a simple ignition module. (and I bought a boat with twins).
I was a USCG Machinery Technician, an ASE certified Master Truck Technician, left that industry for Computer Systems Engineer.
On the SeaRayClub forums we had a similar discussion. I stated I would never own a newer fly by wire boat, never have a Sea Ray with an infamous ECM (controls lighting, winches, pumps, digital helm switches). And many owners of MPI and EFI TBI are always asking for diagnostic help with strange engine behaviors. or No start issues.
I got a lot of guff from saying my engines are critical, all the other electronics, for navigation and such are NOT. In the end my position was and still is. "KISS where I can and redundancy where I cant." I have two VHF, one fancy DSC, one old ICOM 500 mounted below. I only need one engine and my compass and I'll get home.
You cant get out of a boat and walk.
You cant get out of an airplane and walk.
To those that claim electronics if properly designed is reliable you are in denial. The more complex the system the more points of failure and the more failures WILL be experienced.
Go on YouTube and look at how many large "out of control" boats there have been recently, fly by wire? You aren't going to hear about the boats that got towed in from the bay. Nor about the ones that had to get towed in from offshore. You only read about the ones that ended tragically.
737 Max, millions of dollars and man hours; but no button that simply says "My Aircraft".
While a mechanic I had a Penske International DT466E truck towed in that was 100ft away from a lightning strike on an overpass. The truck was NOT hit. But just the Electro Magnetic Pulse was enough to fry the computer and several engine sensors, the FM radio too. Not anecdotal I was the tech that repaired it.
I have seen numerous Detroit 60 series DDEC problems as well. Sure MOST electronic heavy diesel engines are reliable. But they have significantly more issues then non-electronic. I've worked with both.
The auto and light truck diesels are a joke, way to much electronics today.
I have a 2001 Dodge RAM 2500 5.9 24v Cummins, and even it had bad Bosch electronic VP44 pumps. I just lost the alternator, the PCM controls the alternator field (no dedicated regulator) $300 to fix the "voltage regulator". Nuts.
With electronic stuff, electronics on an engine don't concern me much. But electric steering, or electric shift / throttle systems just don't seem to be build robustly and reliably enough for me to be comfortable with them. There's no excuse for it either. Building reliable electronics for fairly simple stuff isn't all that hard.
I see no data on this. The diesel electronics seen to be rock solid . The failure is far more likely from a belt, pump or hose. Not a computer.
Folks, think about the millions of vehicles on the road, all of which are controlled electronically and have been for thirty years. Yet, have we heard about widespread failures of electronic components? Nope. Yes, occasionally, very occasionally someone, car, truck, boat will experience a problem but hardly a reason for concern. I once had to have the injectors replaced on my truck. Soon after leaving the shop, the engine went into limp mode. A computer diagnostic (my own code reader) revealed an open circuit for one injector. Turned out the mechanic had not tightened a wire on one of the injectors. The point is, the code reader revealed the problem. The example cited in another response where a "mechanic" threw $5,000 of parts replacement, just guessing, is merely an example of an incompetent mechanic when it turned out to be a simple harness connection. A code reader would have revealed the open circuit.
Now, the real problem is that some manufacturers have set up their computers such that only a certified mechanic ($$$) can get into the computer to do the diagnostic. John Deere is one. There are many farmers who are not happy with Deere for this reason. There are even bootleg interfaces for getting into Deere computers. Imagine having a combine fail in the middle of a time-senstive harvest, having a propulsion failure, and the nearest Deere factory mechanic is 150 miles away.