After scoring 99 not out and 120 not out on Wednesday opener Jonty Jenner was caught for one off three balls at the start of the second over.
But Sumerauer and Watling put on 65 for the second wicket before the former was caught after hitting six sixes in his 15-ball innings just before the halfway point to leave Old Victorians on 66-2.
Watling hit four sixes in his 18-ball 32 before being caught to leave the Jersey side 89-3 midway through the seventh over.
But Old Victorians’ lower order failed to deliver as they managed just 27 more runs as skipper James Duckett (14) was the only other island batter to make double figures as they ended on a gettable 116-7.
The Scots’ wicketkeeper Callum Garden hit four sixes in a 15-ball 33, but none of his team-mates got past 18 runs as Forfarshire regularly lost wickets.
They lost three in four balls after James Duckett dismissed skipper Jack Hogarth for 10 in the final ball of the seventh over, before Webb took the wickets of Garden and his replacement Lewis James in consecutive balls in the next over.