Youngster TeKaokao Kairimu scored in the corner and Ruapehū had closed the gap to 12-10 at halftime.
Taihape started the second stanza with composure, Whale adding two penalties and then the team scoring their third try, with loose-forward Tremaine Gilbert getting the other five-pointer alongside Whale.
But from 23-10, Ruapehū came back again as Hart forced his way over for a double, with first-five Kahl-Elers Green adding the extras for 23-17, as both Premier games still hung in the balance.
Ultimately, Taihape would see it out as they got a late penalty for Tyler Rogers-Holden to slot and deny Ruapehū even a bonus point for all their efforts, although the nervous times would not last as word came through that Marist hadn't got any extras against Kaierau either.
It means the Ohakune team will make the long trek to South Taranaki to meet Waverley Harvesting Border, who had the weekend off after Settler's Honey Ngamatapouri opted to default their final match in the Waitotara Valley.
Ngamatapouri had only 12 fit players on the field at one stage the previous weekend against Taihape, having lost nearly that many over the course of the season to injury, while standout midfielder Timoci "Jim" Seruwalu is also on stand down after his red card from that game.
In Tasman Tanning Senior, the two finalists have been confirmed with one week of the regular season remaining as undefeated Harvey Round Motors Rātana ended Gemini Pepper Construction Kaierau's last hope 30-10 at the Pā.
All but certain to now hang onto the Stihl Shop Wanganui Challenge Shield for the rest of the campaign, Rātana extended their 13-0 halftime lead to 25-0, and although Kaierau scored late points it was not enough to get back into it.
Also playing to secure their ticket to Cooks Gardens, Ali Arc Logistics-DNA Kennels Marist Celtic had a tough assignment away to Kelso Hunterville, but strong play on either side of halftime took them to a 30-20 victory.
Hunterville had the early advantages, leading 10-5 and then 13-10, before Celtic rattled off three tries, two converted, and added a penalty to pull clear 30-13 with the clock ticking down.
The home side scored a late converted try, but the defeat left them in the unfamiliar position of sixth place, as Bennett's Taihape moved up after a good day for the home sides at Memorial Park, beating cellar-dwellers Border 34-19.
Utiku Old Boys signed off their last home game in style with a 76-14 smashing of a Black Bull Liquor Pirates in their final match of 2020, with Utiku overtaking Kaierau in third spot but too far back to push for a final berth.
At McNab Domain, Speirs Food Marton continued an impressive late season run with their fourth straight victory, beating home side Counties 31-6.
Results, September 5
Tasman Tanning Premier, Week 10
Wanganui Car Centre Kaierau 17 (Tawera Puohotaua, Karl Pascoe, Ethan Robinson tries; Robinson con) bt Dave Hoskin Carriers Marist 7 (Luke Foster try; Ashton Coates con). HT: 7-all.
At Memorial Park: Byford Readimix Taihape 26 (Dane Whale 2, Tremaine Gilbert tries; Whale 2 pen, con, Tyler Rogers-Holden pen) bt McCarthy Transport Ruapehu 17 (Campbell Hart 2, TeKaokao Kairimu tries; Kahl Elers-Green con). HT: 12-10.
Grand Hotel Challenge Shield – Waverley Harvesting Border bt Settlers Honey Ngamatapouri by default.
Central North Island tournament
The Whanganui Collegiate 1st XV's impressive run in the Central North Island (CNI) tournament came to an end after losing a 27-24 semifinal thriller to St Peter's Cambridge on Saturday.
At the neutral Owen Delany Park in Taupō, Collegiate for the second game in a row gave up a try in the opening three minutes, with Cambridge flanker Jonty Short scoring, converted by first-five Dawson Smith.
Collegiate hit back swiftly with a converted try to their own through openside flanker Thomas Pease, before captain and standout first-five Harry Godfrey then scored another try this campaign, which he converted to give his team a 14-7 advantage at the break.
Cambridge came out firing in the second stanza, with winger Anam Farrant dotting down, and although Godfrey slotted a penalty to keep his team's nose ahead 17-12, the Waikato school continued to dominate possession and appeared to have taken control with tries to second-five Quinnlan Tupou and hooker Shayne Retemeyer.
However, Smith couldn't add the extras and trailing 22-17, Collegiate broke through with second-five Shaun O'Leary scoring a converted try for 24-22 with just five minutes remaining.
Cambridge didn't even need two minutes, as from the kickoff they secured possession and Smith scored, and while he again couldn't add the conversion, it was enough as Collegiate ran out of time.
In the other semifinal, for the second season in a row defending champions St Paul's Collegiate ended Feilding High School's title hopes, winning 34-12, meaning both North Region pool sides won their way into the final.
St Peter's Cambridge 27 (J Short, A Farrant, Q Tupou, S Retemeyer, D Smith tries; Smith con) bt Whanganui Collegiate 24 (T Pease, H Godfrey, S O'Leary tries; Godfrey pen, 3 con). HT: 14-7 Collegiate.
