I wasn't assuming the tuners were careless or reckless, I was asking about how they arrived at the changes to the program. OEM tuning involves the same kind of testing as car and truck engines- come up with a basic program to make it run, then test for emissions, in-cylinder gas temperatures, torque/HP, fuel delivery, maximum spark advance to make it run at the correct air:fuel ratio, etc. Then, they go to a body of water for all kinds of testing that includes destruction of the engine & drive. Some manufacturers have their own water (Merc has Lake X, Mastercraft has their own on company property in Tennessee) and others go to local water but having their own removes distractions and assures continuity. If they can't make it fail, it's likely that most boat owners won't either, but there's no reason to assume that someone can't.
My friend who worked at the GM Desert Proving Ground drove cars on their 5 mile track without oil, sometimes without coolant- they drove the cars until they dropped, towed them back to the shop and made the repairs, then went back out after some kind of change was made and that included engines and transmissions. Sometimes, a problem will show up after the boats had been validated and sold, but wasn't expected- hot start issues in places with high ambient temperatures was one examplet they gave- once they corrected the high temp trigger after heat soak, the problem was gone.
All ECM programs have a checksum, to tell the tech using a diagnostic computer/analyser the version of the program- the old program should be saved, in case the engine needs to revert to OEM, since tuning without all of the testing
I joined another boat forum because someone posted their idea of a solution to the warning buzzer that only ran around the first few seconds after startup- "Just cut the wire to the buzzer". This was a new boat and that would have voided the warranty. Since I joined that forum, I learned that a lot of people use the 'parts cannon' when they try to diagnose a problem. There's absolutely no knowledge of the systems on a boat or the chain of events during crank, run, failure modes or anything, they just replace parts until they make the problem go away, or not, and often by replacing several parts in one step. They think they found a definitive answer but they didn't understand that in their group part replacement, they completely eliminated any possibility of certainty in knowing the cause.
The boat owners on that forum would never consider touching their car or truck, regardless of the value but they were confident enough in their abilities that they dove head first into horsing around with a boat that, at the time, sold for over $75K. However, it wasn't just about not wanting to pay the price for service, the problem was that they didn't have an authorized dealer nearby because they used their boats in remote areas. Still, they could have gone to a GM dealer and found a quicker solution and not voided their warranties. Unfortunately, not all of the 'authorized' dealers kept the techs who had been trained by the company and the remaining people didn't have/use the shop manuals, nor did they have a clue of their own- boat dealers are well known for being too cheap to train people because they see the time away from the shop and money paid for travel & lodging as "It costs too much" without considering the positive effects from the training. Coming away from training, making new contacts, learning tricks that make diagnostics much easier and being able to repair boats in one trip to the shop without returns for correcting mistakes, damage to the boat or handling PO'd customers doesn't seem like a cost, to me.
One problem that was caused by COVID- in person training was ended for many brands and without the face to face communication at the time of presentation, a lot was lost at a time when boat technology is increasing at a high rate.
