Obi is trialling with United this month, along with West Ham United winger Oscar Borg.
Jordan Thompson lashed in the opening goal following a cross by Ogo Obi, executing a textbook volley.
Another Obi centre led to the second goal as Demetri Mitchell made it five goals for the tournament by swiveling to score. Marcus Rashford and Mitchell had further opportunities to find the net but the floodgates did not open.
Rashford did get in on the act with a solo effort to put the seal on another fine victory for Paul McGuinness' side.
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