TAMD 74 EDC not starting

Hello,
I am Oliver and our boat in Croatia has a problem with one machine.
It would be very nice if we could here someone assist in troubleshooting or valuable tips for analysis.
The motor data:
2x TAMD 74 EDC; Engine No. 2071 1557. 55; and 2071 1557 54; 2. the following occurs:
Engine start after the winter break without problems, both machines are running properly. After a few minutes circuit to "neutral" and speed slowly increased to about 1000 U / min to drive the engines warm.
Suddenly going all ads concerning the instruments of starboard engine to "0". the engine is running but without problem - speed can be changed in "N" position.
After reaching the operating temperature (display only on the port engine) the machine tries remedy. Portside engine ok. Starboard engine no reaction! Had to manually stop the engine compartment and on the injection pump.
An attempted restart has not been possible since the ignition switch is no voltage!
The review found that the automatic backup on "terminal box" (located on the side of the engine) was triggered.
After again push the machines I've tried restarting.
Immediately after switch in position "1" of the ignition key - without to position "2" next switch, the temperature gauge went up to stop up and securing sparked again - at the same time there was a whistle.
Thus, the trial was terminated. Have the engine to cool down and try the same thing again, always the same result.
Finally, I've checked the coolant level and refilled about 1.5 liters.
I suspect that either the coolant temperature sensor for the instrument or defect for the EDC.

Maybe someone can help me where the fault is to be found, above all, as the troubleshooting can be constructed useful here.

Thank you so much!
Greeting Oliver