Missing five players on international duty, Victory - also without the injured Kosta Barbarouses - were sluggish and fell behind in the 32nd minute after Isaka Cernak headed home.
Cernak, a former Victory player, saw his goal cancelled out five minutes before the break as Finkler curled in an excellent effort from the edge of the penalty area.
And the Brazilian was not done yet, bagging a 77th-minute winner with another curling strike that left Mariners goalkeeper Liam Reddy with no chance.
Kevin Muscat's men sit second in the table, one point behind Wellington Phoenix, who they face next week in a mouth-watering clash.
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