I'd raise all sorts of hell if I were that customer. That's insane.
Granted, my wife's car had an issue after she filled up at a gas station. I told her it was probably bad gas as we had had ZERO issues with the vehicle and it only had 40k miles on it. Took it to a mechanic just to take a look and they told me that since it was under warranty (100k mile drivetrain) that I should take it to the dealer. I hate taking vehicles to the dealer. They are usually inept, but whatever the issue it would be fixed for free.
The service guy (who's job I can only assume is to not know things and forget to call back) told me the intake was broken (even though the vehicle ran and had no codes) and that it wasn't covered. Not too expensive so I let them fix it. 3 WEEKS later they have replaced the head on the vehicle (known issue with the previous year model) and told me they finally fixed the problem...it was bad gas. I told the service guy moron that when I took it in. He forgot and told my wife that "it would have been nice to know" when they got the vehicle. I haven't stopped trashing them to anyone that will listen.
It's unfortunate, but the marine industry has a lot of bad techs and in some places, they just move from place to place, rather than leave the business or get some training. First time I went, we had a day of electrical training that included wiring a Bosch relay to switch between a bilge blower and a light. I had worked with car audio & security for over 20 years, so it was no big deal. The group fighting with it before me had no.freaking. idea. what the relay did, how it worked or how to wire it. Apparently, they had great reputations for service, but only if the engine had a carb. The instructor saw me sitting at a desk and asked what I was doing. I told him I was waiting for the relay rig and after he said I should report back in a few if they weren't done, I asked if it would be OK to draw a diagram, so I did. That took all of ten seconds and when he saw this, he asked me to help the other group.
The bad ECT tells me the tech never went to service for fuel injection because it's one of the senders that affects performance the most.
I heard about fuel quality problems in this area and started taking the receipt every time I buy- that way, I have proof of where the gas was bought and when.
You would be amazed by the number of people who own boats that cost over $60K (many over $100K) and would never think of touching their car or truck, but they jump in head first on the boat at the first hint of trouble and the fact that they know absolutely nothing about how to troubleshoot it has no impact on this. the first thing they do is break out the parts cannon and start firing. Eventually, they can fix it, but when they replace all of the sensors, plugs, wires and other small parts, there's no way to be certain about what caused it.