ok, i put a extended explanation in the plcs in boat.
just now a smalle explanation.
I was a process developer in the chemical industrie and we found that plc are very stable even for hard temp/vibration, ect. situations
I use the siemens logo system first its not so costly, you can use it for a lot, and i have the programmable software (i program them for the last 14 years)
On my boat hey have the following functions :
1. monitoring the motor exhaust tube temperature
2. monitoring the service bat capacity and (if selected) start/stop the generator.
3. control the bilg pumps and if they run to long phone me with a warning, if they run at critical time keep phoning till some anser or connect to the port security.
4. control timing for the side gang lights.
5. give a warning for refill check of the service battery (all on screen)
6. give a warning or phone if the 220v service get off line (for the coolers)
just making it safe and better control when not on board.