Old system New owner

Hello folks, I have a solar system on a boat that I purchased. Could use feedback on charge controllers. Thanks. The system is old and janky. No fuses, no charge controllers. It's three panels going to a 12 volt bus bar which comes off the battery. There is a amp meter in line and I have measured the volts of the combined panels. It's never over 15 amps and volts hover around 18 to 20. The panels are old and different. No stickers you can read and the panels are hardwired together IE no connectors. I really want to straighten this mess out but am not sure where to start. Getting to the boxes on the back of the panels is a PIA and I realize I may have to do this to get individual reading. From what I have picked up so far my best bet is three individual charge controllers going into the bank. PWM would be the choice as three MPPTs would be way to costly. The battery bank is 4 Trojan T105s linked for 12 volts. So far I have not had any issue with lack of power but having three panels going into the system at a bus bar seems a bit janky. Plus i don't want to leave the boat unattended. I live on it so I can, in theory,monitor the system.
On a second note: when I do an amp reading on each panel, with a clamp on meter, would I have to disconnect each panel and then connect to a battery to get an amp reading? Thanks in advance.
John Conway
FL as in too hot Keys