Flanker Kobe Rogers scored to give West a comfortable 17-0 lead at halftime.
Any chance of a comeback by East was shattered as Karauria and winger Lachlan Haycock quickly stretched the score out to 27-0.
East finally had something to show for their efforts when No8 Mileno Fotu charged down a clearing kick by Karauria to score but his opposite Neitana Tapiata-Smith had the final laugh when he crossed unopposed from a scrum.
Tauranga West head coach Geoff Booth was pleased with how his team stepped up from their earlier performances.
"In that first game [against Tauranga East] they fed off our mistakes and we couldn't get any flow and build pressure, so the tournament has been about let's build pressure," Booth said.
"We don't have to score off the first phase and today I thought we built pressure really well. 'The boys realise they have to go five or six phases before they can cross the line, and that is the one key difference today."
In other results, Whakatane beat Rotorua Gold 29-26 and Opotiki thumped Rangataiki 71-0.
Finals day at Blake Park today starts at 9.30am with the Bill Murray Trophy playoffs, followed by the Gavin Parkinson Trophy and Rob Shaw Cup games at 11am before the Tai Mitchell final at 12.30pm.
Results:
Tauranga West 34 (Jack Broadley-Ryan, Eldo Pasi, Kobe Rogers, Logan Karauria, Lachlan Haycock, Neitana Tapiata-Smith tries; Jay Gardiner 2 cons) Tauranga East 5 (Mileno Fotu try).
Te Puke 22 (Coolio Williams, Tre Pohipi, Tamikoha Te Aute tries; Wipori Tuanau 2 cons, pen) Rotorua 7.