Mount was not done though, and managed to conjure up a comeback on the back of some attractive running rugby.
Mount wing Leini Hakamotu, who plays in a manner not too dissimilar to Inga Tuigamala, was heavily involved.
He barged over from close range after a number of fine touches, before inside back Sioeli Faaui capped a strong display by blowing over the top of the Opotiki cover defence in the corner as time expired.
The conversion made it 20-18, with Opotiki running out winners thanks mainly to a strong forward effort.
Opotiki College coach Richie Howe was glad to have got off to a winning start.
"A win's a win, so we'll take it," said Howe.
"It was the first game of the season, we got a lot out of it, but a lot of improvement is needed. We should have put them away but we let them back in. I went to the bench, made a few changes, and I think the game changed."
Opotiki College 20 (Karl Smith 2, Tukakae Tahau tries; Kaleb Maxwell con, pen) beat Mount Maunganui 18 (Sioeli Faaui, Leini Hakamotu tries; Bill Carter 2 pens, Daniel Pushart con)