I have this Garmin unit which I'm very happy with but the Screen's just not reliable anymore .... goes off on its own sometimes, screen impossible to read others .... I wouldn't mind buying a replacement, but I'd like to just replace the unit, not the piece that sits under the boat, or the power supply, or the wiring. Does anyone know if a newer Garmin or other unit would be compatible with the existing hardware? Thx much, DMiller