Suddenly shutting off simultaneously both engines DDEC III 16v92

White Hat, I have a very similar issue with my 1994 Ocean with 8v92's. Have ddec 2 system. I would start boat and let her warm up. After 20 -40 min or so, controls would suddenly go to neutral and low idle. I could not reset engines via active station as red light would go out. No codes or anything on control heads. I would shut engines down, wait 2 seconds and restart. Same thing would happen now at 10 min. Repeat process and it would go to emergency mode every 2 - 3 min. If I turned system on but did not start engines, it would stay on for days. As soon as I started engines, the emergency mode process would start. I did not loose power to my control heads.
I went so far as to only run one engine at a time. Found out that my issue is related to the starboard output side from the ERIM. I had sent mine back to Sturdy where they bench tested. They could not duplicate my issue. I also interchanged the CSIM's and active control units(did not fix issue). I even swapped wiring harness connections into ERIM(port engine would run off of starboard output) and then port would go to emergency mode. If I was running both engines at same time, they both would go to emergency mode.
I have just received another ERIM(the exact one you have pictured). Have not installed it yet as boat is now winterized.
You might confirm with Sturdy about your DDEC system as they told me that unit is a DDEC 2.5.
It will be interesting to see what you find out as to your problem. I did not check any relay on fire boy system but will.
I won't be able to install new unit until sometime in March when I re-commission her.
Let us know how you make out.

so, what happens in case where the system relay or other malfunction shuts down the engines just as the boat is coming into the dock area, no brakes people on outer deck big bump big damage maybe broken bones ?

If you are like me, as soon as I had the issue, you do not leave the dock until the problem is solved. Boat has been sitting at dock and all tests are done there.
Insurance companies and neighbors don't like crashes!

Rcrapps. It depends. In all the years, I can't remember of a single time I had a DDEC engine issue resulting from the ddec stuff. As far as I know MTU is still using the DDEC electronics (while updated) currently today. It's been in the electronic controls side where most issues are, they're manufactured by Sturdy. One of the issues I had resulted from the shifter cables adjusted wrong where they connected to the electronic solenoid.

I'm seeing a few issues, but not nearly that often. There's positives and negatives. The computer controlled motors start right up everytime, they run clean, they're fuel efficient, etc. etc. My biggest issue is having to cut dashes to install smartcraft vessel view 7" screens to replace the old lcd displays that are smaller and now unreadable. Had one cat palm beach style throttle control go bad.

Had a lot of what I thought were DDEC control issues on an arneson boat but turned out the props overloaded the motors unless the drives were fully up and the boat is underway for 150'. Putting them in gear RPMs dropped to 440rpms and no throttle, computer couldn't get the motors over 500 rpms because of load and unless the motors see 500 rpms they won't give them throttle.

What is a code 58 overload?