I have an EVC comms issue. I have two engines, other one works well. Can I test the EVC unit itself simply by switching them and looking if the issue moves to another side? The reason to ask is that I do not want to mess the working unit if there is a risk of that when interchanging. They are apparently programmed to individual engine serial number.
If you have a flybridge the connecting cables, at this age, sometimes corrode. Do a simple test on the cables first and only then switch the EVCs.