And when Yovich holed out on the long-on boundary off Fletcher Coutts for an enterprising 57 off 49, Onerahi had a real chance to limit City to a beatable target.
But the injection of Harry Darkins (29 off 27) and Matt Lobb (32 off 17) gave City the impetus to set a challenging total.
Lobb smashed three sixes - including a booming drive straight over bowler Anders' head - to help City to a total of 148/4 off 20 overs.
Onerahi started well with captain Brad Kneebone (22) and fellow opener Todd Beehre (17) getting them off to a good start.
However, both were removed in quick succession by off-spinners Ryan Brown and Thompson to leave Onerahi at 43/2.
Little then removed Charlie Roebuck for 6 which gave City a sniff, but Onerahi pushed forward with Henry Cooper and Anders (22) combining for a 56-run partnership to put them within striking distance of the target.
Cooper was particularly impressive in his 45-ball 57, showing why he recently made his first class debut for Northern Districts.
But Yovich (2 for 19) came on to bowl and removed both Anders and Cooper, leaving Onerahi needing 25 from three overs.
There was a bit of tension but Coutts and Tom Herman saw Onerahi home with just one ball to spare.
City's reserve team wasn't spared by Kamo as they were rolled for 59 en route to a 68-run loss.
James Cherrington continued his good form with 38 as he steered Kamo to a target of 127 on what was very much a bowler's wicket.
James Smith (3 for 17) was highly effective opening the bowling while a five-wicket bag from Barry Newton (5 for 24) proved to be a nuisance.
City would have liked their chances but a real team effort with the ball from Kamo ensured City never really got going.
Logan Choat, Hero Singh, Curtis Cherrington and Richard Cates each grabbed a brace to rip through City's batting order, giving them their second win in the 40-over competition.
Other reserve grade results saw Whangarei Boys' High School Second XI beat Kerikeri and Onerahi snatch an intense one-wicket win over Kamo High School.
Kerikeri batted first against WBHS and set an imposing 217 all out thanks to contributions for Owen Arthur (58) and Aaron Ranara (42).
Tim Osbaldistan was the best of the WBHS attack with 5 for 16.
WBHS then went about chasing down the mark, led by an impressive 83 from Dante Mitchell.
Then Richard Stobart (30 not out) and Craig Gurr (20 not out) saw WBHS home with five wickets to spare.
In the other clash Kamo High set Onerahi a target of 195/8 from their 40 overs after Sam Webb (54) and Harry Cooper (41) rescued them after drinks.
Onerahi captain Adam Sylva led the bowlers with 3 for 42.
In reply, Onerahi got contributions from Ryan Woodman (24), Dev Birchell (24 and Pieter Lambrechts (21) but found themselves needing 40 runs from their final wicket partnership.
Max Turner (2 for 33) and Billy Alexander-Crawford (2 for 33) helped Kamo restrict the majority of their batting order.
But captain Sylva (39 not out) combined with number 11 Axel Sheppard (6 not out) and saw Onerahi home in a tense finish.
*other results were not received by the deadline