DDEC's are the big exception for Detroit. They're normally a great company when it comes to providing factory parts support for their products well past the point where Cummins, CAT, Volvo, MAN, or anyone else would be laughing at you. But these are different, they were so problematic that DD washed their hands of it and walked away. Virtually all of the parts for the DDEC systems have been NLA for years with no plans to resume support.
So you're stuck with $10k replacement displays, $15k replacement ECM's, and that's when you can even find them. There are sensors you can't get, wire harnesses you can't get, and the only support for any of it is a small number of aftermarket electronic repair guys who may or may not be able to fix to your problem. The displays are usually repairable at high expense, but the rest is a coin toss.
Most mechanics won't work on DDEC's for two reasons. One is you need a proprietary diagnostic computer and software subscription that's expensive, but the main one is because in the end they just end up with pissed off customers and a boat that still doesn't work because you can't get parts. The final version of DDEC from the 2000's was by most accounts reliable, but it had such a bad reputation that everybody was avoiding it by then so there aren't many out there.
YMMV, but personally I would never own a DDEC boat.
