The longest marathon playing a board game is 61 hours and 2 minutes, achieved by Brett Carow and Sam Hennemann (both USA), in New York, New York, USA, on 7-9 June 2012.
They played Strat-O-Matic Baseball. During the attempt 116 games were played. They began at 9 am on 7 June 2012 and ended at 10.02 pm on 9 June 2012.
Comments below may relate to previous holders of this record.