Lot of questions. The biggest question is what kind of power does your motor need? How big is the motor? How far do you intend to motor? Is this a DIY job or did you buy a system from a manufacturer?
Series wiring will increase voltage but the amperage will remain the same. Parallel wiring does the opposite, voltage remains the same, with the amperage will increase.
With the 4 batteries you have, you can get 80 ah at 48 v if all four are in series. Or 320 ah at 12 v in parallel. Or you can get 24 volts and 160 ah if you have 2 pair of batteries wired in series and each pair wired in parallel.
Regardless of the configuration, the battery capacity you have is likely very inadequate for the electric motor if you intend to motor any distance, meaning more than just motoring out of the marina.
An 80 ah battery has only 40 usable amphours. Thus, if maxed out the 320 ah you have has only 160 ah that are usable.
The amount of solar you will need will depend on how big the battery bank is. As a guide line you can expect on average to get 3 times the nominal capacity of the panel per day, i.e., a 100 watt panel can be expected to provide 300 watt hours of power per day, more on bright sunny days in the summer, much less to zero on cloudy days. Once you know the amount of power you need for the motor, you can determine the battery size, then you can match your charging sources to your power needs.
Edits: Corrections in blue.