In the first half, his dash set up halfback Trent Reti (Horowhenua-Kapiti) going across, which was book-ended by two very good Tasman tries from midfield breaks.
Korotimana started the big rumble to the line for Heartland in the second half, and after No8 Logan Winter (West Coast) went close, Korotimana picked it up again and smashed over.
Running with the ball in one hand, Korotimana went off the back of a 30m scrum and with three defenders on him made the flick pass to fullback and captain Josh Turner (Thames Valley), who scored in the corner.
First-five Bryce Shearer (South Canterbury) added two conversions and two penalties.
"We were underestimated coming into this comp with only two days training, but the boy's really dug deep," said Turner afterwards.
Heartland were facing Southland yesterday with the winner going on to the trophy final against either Hawke's Bay or Manawatu.