2001 marlin questions

I just bought a 2001 Marlin 30 and it came with a Furuno Color LCD Sounder FCV-582-L, a Furuno Radar Model 1731 Mark -3 RDP-099 and a Garmin 740S Plotter sounder. The boat was a one owner, well maintained boat, excellent shape. The Furuno equipment does not seem to work as well as I would have...