we went through this when we first bought a boat new or sccond hand at the end of the day we found second hand was just buying someone else s problems or it had come to the end of its useful life buy new electrics they are garanted and you will get mssi number dedicated to your boat link it to your gps and heven forbid if you get into a life threatening situation just press the button if you have no time for anything else they have your positon boat name and someone is coming to help
Totally agree and have vowed never to be tempted again, had 2 radios both binned and an ST4000 wheel pilot which had to have compleat replacement board (although in this case it was worth what I paid for the drive unit).
Can recomend Icom for radio, not only does it work better than most (ie you get clear reception in areas where other radios get noise) but also the screens and buttons are big enough to see in dim light without glasses and work with cold gloved hands! Big chunky and built like the proverbial BSHouse is good for anything that may be used in an emergency