The young Blues went up against Accrington Stanley in their first away game of the new league season.
And they came from behind for the second weekend in a row to claim an excellent and convincing away victory.
Stanley went into the break with a 2-1 advantage but goals from Kerr (2), Galloway and McCarron earned United their deserved victory on a warm day in Lancashire.
Youth boss Darren Edmondson said: "It was an excellent second half performance.
"Accrington had the lead against the run of play at half time but we stepped things up and we scored some good goals.
"We showed that we had more energy and desire and, with no disrespect to them, we could have scored a few more."