I'm going to be moving my boat to a dock that does not have electricity and need a way to hook up my battery charger. I know it can be done, but don't know how to size the solar panels to have enough power to charge/maintain batteries. I am running a 2 battery, 24 volt trolling motor system.

Any thoughts?

See what draw your charger needs then get enough panel to run it. If your wanting to have it maintain 24-7 then you'll need battery banks and other equip that way your still charging at night and on cloudy days.
Otherwise just the correct sized solar panel and a voltage regulator.