Two-times winners Merrion advanced safely to the quarter-finals of the Irish Senior Cup as the made light work of a potentially tricky 249 target in the replayed match at Anglesea Road.
YM's total of 248 for 9 was boosted by late runs down the order, plus 30 wides and 2 no-balls.
Tom Anders top-scored with 46, sharing a sixth wicket stand of 69 with his brother Rory (29) while Mikey O'Reilly made a run-a-ball 28 not out from number 10.
O'Reilly then struck twice to remove Stephen Doheny and John Anderson cheaply.
That was the high point for YM as Swapnil Modgill and Sam Harbinson quickly took the contest away from them. Modgill made a brilliant 112 from 98 balls (13 fours, 4 sixes), adding 134 in 23 overs with Harbinson - whose undefeated 92 included 7 fours and a six.
Jack Carty (26*) added a further 78 with Harbinson as the 7 wickets win was sealed with five overs to spare.
Merrion now travel to Waringstown in a real heavyweight clash - the sides having met in the final three times in recent years.