2014 Bennington 2050RL Electrical Issues

Hello all, fairly new to boating in general here. I inherited a 2014 Bennington 2050RL pontoon with Yamaha T50 motor. The boat has some electrical gremlins, and i am wondering where to start looking. The fuel guage always reads empty, but will sometimes bounce up when pressing the horn... the voltage meter will sometimes read low when it's not, or will bounce around, it will go up to almost showing 14 volts when you turn lights on. The depth finder is also wonky and shows random depths sometimes. The battery terminals are free of corrosion. Never popped any breakers on the boat. Never has any issue firing up the motor.

I am guessing all these problems are somewhat related. Possibly a bad ground? Any suggestions on where to start digging? Thank you in advance.