East Coast will play Wanganui, which came from behind to beat Mid Canterbury 32-22 and progress to a sixth Meads Cup final.
North Otago went into the semifinal with the knowledge it had beaten East Coast earlier in the competition, 52-17, but found the task of repeating the performance a bridge too far.
East Coast was able to dictate and control the pace of the game and this served to frustrate North Otago.
When the Old Golds gained possession, they were seldom able to build up multiple phases before a pushed pass or mishandling gave the ball back to East Coast.
North Otago coach Barry Matthews was philosophical after the game.
"East Coast thoroughly deserved its win. They had the self-belief and they played to their strengths and we probably never played to ours."
North Otago held its own in the scrum while tighthead Palenapa Mafi was on the field, but when he left, North Otago lost that control.
"Mafi did play well but we had to bring on Aisake Fonua, who I thought played well in the front row against Mid Canterbury. To be fair, we've had trouble at scrum time all year," Matthews said.
"I think last week our scrum was under pressure to such an extent that Hamish McKenzie passed the ball from halfback on only three occasions, such was the pressure on us. It makes it very hard for the halfback when the scrum is twisting and turning to set a platform."
North Otago needed to hold the ball for four or five phases to open up East Coast but through pushed passes or the taking of wrong options too often the opportunity was lost.
The bulky East Coast pack competed well in the linouts through Willie Waitoa, who picked up a couple against the throw, while the visiting side's mauling power and ability to hold on to the ball for long periods of time denied North Otago momentum.
Second five-eighth Rua Tipoki was the organiser on attack and defence, while fullback Sikeli Vorenasu showed blistering speed to score two tries and set up a third.
Luke Herden was again in outstanding form for North Otago, setting up two tries as well as defending stoutly.
East Coast hit North Otago early, with Vorenasu scooping up a loose pass to race 40m for the opening try.
Tidy first five Clayton Kiwara added a penalty eight minutes later and, two minutes after that, Vorenasu slipped down the right flank. He centre kicked and hooker Ngarimu Simpkins gathered to score beside the posts. Kiwara's conversion gave East Coast a 15-0 lead after 16 minutes.
North Otago strung together some phases and a Hamish McKenzie kick into the box was gathered by Mafi. The supporting Herden sent Faaitu Tuamoheloa in for a try.
Eleven minutes from halftime, Ralph Darling took a tap penalty and a half-break by Herden put the flying Whiria Meltzer into the clear on a 50m run to the line.
North Otago took the lead with a Patston penalty, and then East Coast was temporarily reduced to 13 men when Simpkins and Waitoa were sin-binned.
But East Coast controlled possession and regained the lead with a Kiwara penalty.
With 17 minutes remaining, a bit of Tipoki magic created space for Vorenasu and the fullback raced 55m to chip ahead and score his second try. East Coast then shut up shop and ran down the clock.
Both Lochore Cup semifinals went to the wire, with South Canterbury beating Thames Valley 30-27, and Poverty Bay beating Buller 32-20. The final will be in Timaru.
THE SCORES:
Heartland Championship
• East Coast 23
Sikeli Vorenasu 2, Ngarimu Simpkins tries; Clayton Kiwara con, 2 pen
• North Otago 17
Faaitu Tuamoheloa, Whiria Meltzer tries; Ben Patston 2 con, pen
• Halftime: East Coast 15-14.
