The round two thriller went down to the wire, as Numurkah reeled in United's score in the last over with two wickets in hand.
After United elected to bat first at Princess Park, the home side posted 7-83.
Numurkah's Riley Dawson then led the charge for his side with a stunning 20 not out.
Dawson top-scored while United's bowling stocks - spearheaded by Spencer Dickins (1-2) - tried to restrict the Blues to less than their total.
But Dawson's Blues were able to grind out the win that moved them atop the A-grade ladder.
Meanwhile, Ethan Beck (51 not out) raised the bat with an impressive half-century in Notre Dame-St Brendan's Gold's 48-run win against Euroa.
Beck's superb knock came off 54 deliveries, with six fours and one maximum.
Fellow opening batsman Mason Reeves hit a quick-fire 44 off 34 deliveries and smashed seven boundaries.
In reply, Euroa's Cohen Paul top-scored with 19 as the Magpies finished with 5-107 off 25 overs.
Old Students prevailed against Tatura at Central Park Recreation Reserve with a comfortable 68-run victory.
The Students’ Mitchell Higgins top-scored with a dazzling 28 not out, whacking four boundaries off 20 deliveries.
And teammate Harper Collins proved to much to handle for Tatura's batting line-up, picking up 2-1 off his two overs.
● Elsewhere, Northerners’ Cohan Hall hit a sublime 36 in his side's 79-run win against Toolamba in their B-grade contest at Bunbartha Recreation Reserve.
Lachlan Malcolm (25 not out) provided a classy cameo in the 4-156 first innings, while Ben O'Connell (2-7) was damaging with the ball for the Taipans.
However, the day belonged to Hall, who finished with incredible bowling figures of 2-1 as Toolamba ended its run chase at 7-77.
Lastly, Old Students saluted against Nagambie by four wickets and Waaia powered past Pine Lodge-Karramomus by eight wickets.
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