Coming into the match 19 points ahead of the ninth-placed Phoenix, the gulf in class showed as Graham Arnold's men extended their unbeaten run to seven games.
Nigeria-born Australia Under-20 international Ibini was the star performer with captain John Hutchinson, Daniel McBreen and Mitchell Duke also getting on the scoresheet.
Ibini's opener came after 30 minutes when he capitalised after Joshua Rose's pass deflected off Phoenix skipper Andrew Durante into his path.
Wellington came close to an equaliser six minutes later but Isaka Cernak's long-range effort was turned away by Mariners goalkeeper Mat Ryan.
The New Zealanders threatened again shortly after, with defender Trent Sainsbury having to divert Jeremy Brockie's glancing header on to the bar and away to safety.
The Mariners required a second goal to kill the game off and it arrived via Hutchinson in the 65th minute after good work from Mile Sterjovski.
It was soon 3-0 as McBreen scored his 15th goal of the season when he drilled a header home courtesy of a Michael McGlinchey corner.
The Mariners remained on the front foot with Ibini scoring his second after latching on to a ball from McBreen to finish with his left foot.
And substitute Duke rounded off the win in the 89th minute with his third goal of the season.