Second five Anastasia Tusani added her name to the sheet after good lead-up work, with play staying in Whanganui's half.
The home side finally started to get some traction, standout second five Diaz Gabriel and lock Maina Gray had a crack, but defence, turnovers and counter-rucking prevented a reply score.
Right on halftime, Centurions prop Wynter Ta'ape broke through and ran 40m to score near the posts, halfback Kei Roffey converting for 17-0.
With a slight breeze behind them, Whanganui started to get some traction as Gabriel brought them onto the attack, and two attacking penalties later, she got the ball from a quick tap and dived through to score, flanker Samara Pahl-Long converting.
However, trying to run out of their half saw Whanganui lose possession, and from an attacking scrum, Centurions reserve Breana Nepia sneaked the ball from the side of the ruck to place it on the paint.
Whanganui then pressured Centurions, leading to a fumble, and after attacking down both touchlines, No 8 Cienna Newland went from the ruck to drag tacklers over with her for 22-12.
But that was the end of the rally, as following sustained buildup, Ta'ape went through again to score, and then when Whanganui were reduced to 14 for a professional foul yellow card on their tryline, lock Eva Maora took the quick tap and forced the ball, Roffey converting.
Whanganui U16
In the first of their two pre-season games before the Hurricanes Youth Council tournament next month, Whanganui U16 made a good start with first five Jaydis Hammond slotting a penalty.
But from there, Wellington 3rd XV took over, with centre Callum Connell scoring in the corner and big midfielder Va'a Tui diving over beside the posts.
Fullback Tane Robinson dashed over on the far side of the field for 17-3 at halftime, then in the second half, Connell scored a brilliant individual try beating multiple defenders untouched.
That opened the floodgates, as midfielder Evan Paenga was tackled short but not held to get up and go again for the try, then reserve Jabez Bryce rampaged down the far touch to swipe away defenders and run back under the posts.
With Wellington rotating their bench, reserve Labront Mudbrick ran off a great pass to step under the posts, then prop Marley Fretton and Tui again scored short-range tries after the sustained build-up in the danger zone.
First five Eden Govind slotted seven conversions for a profitable afternoon.