Travis Friend smashed a record-breaking 227 for Castletown as they recorded an impressive 319-run victory over Ramsey in the Premiership on Saturday.
The all-rounder hit 29 fours and five sixes to overtake John McLean's 1985 record of 204.
Zimbabwean Friend shared a partnership of 192 with Gareth Morris, who made 77 as the Southerners reached 380-2 from their 50 overs.
Town then dismissed Ramsey for just 61 to stay top by four points.
Meanwhile, St John's kept up the pressure on Castletown with a five-wicket win over Crosby.