Sewerby entertained fellow strugglers York 2nds on Saturday and on winning the toss asked them to bat first.
A good opening spell from Russ Robinson and Ben Dobson saw the visitors at 27/3 after 12 overs.
A stand of 84 between Sam Beales and Keiran Bloor helped them recover to 111 before Dom Warters recorded his first York Senior League wicket to have Beales stumped by Mark Tennant for 46.
Bloor was run out shortly afterwards for 45 and Shaun Acton and Warters kept the runs down to three an over but the return of opening bowlers Robinson and Dobson saw Ben Horseman (39) and Matt Hodsdon (38) score 50 from the last five overs to take York to 208/8 at the end of their innings.
Robinson finished with 4-59 and Warters a very creditable 1-49 from 13 overs of spin, while keeper Tennant took three catches as well as his stumping.
Openers Sam and Mark Tennant set off at a brisk pace and 43 runs came from the first seven overs before Sam was out for 24 and Mark for 9.
Mike Artley and Dobson settled in steadily and added 47 before Artley was given out lbw for 23.
Russ Robinson joined Dobson and these two destroyed the York bowling, Dobson hitting 85 from 83 balls with 17 fours, and Robinson adding 50 from 52 balls with 10 fours and a 6sixto take Sewerby to the brink of victory.
The result was duly completed without further loss of wickets and with 15 overs to spare.