The southpaw Armyman from Zamboanga, who turned 24 yesterday, pulled away from a slim 1-0 lead in the first round, pummeling Jon Sang Ryol with a series of three-punch attacks to become the first finalist with a whopping 11-3 win.
But two other Filipino boxers lost their respective bouts, all victims of bum decisions.
Ferdie Gamo, despite registering the clearer hits and staggering Korean bantamweight Kim Won II with head shots, bowed out, losing 8-19.
As if to add insult to the injury, No. 1 Korean lightweight Kim Kuang II used his head to put out Anthony Igusquiza in the second round.
The fight was stopped by the ring physician after the Filipino, leading in the scorecard at 5-1, sustained a deep cut in his left eye from a headbutt which the Korean referee simply disregarded, eliciting a mixture of howls and cheers from the gallery.
"Talagang protektado nila ang mga No. 1 nila, gagawin talaga ang lahat huwag lang magalit yung mga officials nila," said head coach George Caliwan whose protest was thrown out.
The twin losses left Team Caltex Philippines with only three survivors.
Aside from Tanamor who will face Korean No. 1 Kim Chol San in the finals, fly Violito Payla and middleweight Maraon Golez remained in the hunt for the gold in this four-nation, six-team tournament.
Payla and Golez go for the finals berths today when they face Koreans Sin kyong II and Yong So, respectively.
Earlier, featherweight Roel Laguna and light middleweight Christopher Camat lost their semifinal matches to settle for the bronze medals.