It was the Royals’ third win of the season and they now sit seventh on the table with 10 points, three points adrift of Nelson in fourth place, who they play next week.
The Royals dominated the first half at Tahuna Park and Selwyn were forced to start a counterattack using long balls through.
The breakthrough goal came as halftime approached with Raven August attacking down the right side, beating his marker and getting down the wing.
Looking up, he spotted Will Turner making a well-timed run that allowed August to lay the ball off to Turner for a tap in, giving the Royals a 1-0 lead at halftime.
Oban Hawkins and Nicolas Zambrano scored for the home side in the second half and cemented the win.
The top of the table in the Southern League remains unchanged with Cashmere Tech, Christchurch United and Coastal Spirit separated by only two points.
Cashmere Tech won a close encounter 3-2 at Ferrymead Bays.
Christchurch United beat Nelson 4-0 with former Green Island players Joel Stevens and Matt Brazier scoring three of the goals.
Coastal spirit had an emphatic 7-0 victory over FC Twenty 11, who had keeper Harri Rowe sent off for collecting two yellow cards in the fourth and fifth minutes of stoppage time.
Hunter Hines’ injury-time equaliser gave Canterbury University a 1-1 draw with Nomads, moving them four points clear of the bottom-placed FC Twenty 11.
By Neville Watson
