"I trained hard, we put the effort in," Serepisos said after the final.
He trained twice a day during the lead-up to the tournament, including running and pad work.
It was a frustrating night for the veteran Vannathy who had hoped to finish with a bang in his hometown.
The 34-year-old has signaled he is near the end of a 20-year kickboxing career and although he has a handful of bouts left, last night's event was likely his last showing in Porirua.
"Thank you very much for coming to support me," he said in the ring after his fight with Serepisos.
"I was hoping to finish it in a nice fashion but it didn't go my way; apologies."
Vannathy had nothing to apologise for though, given his contribution to the sport, which continues through the coaching he does with young people in the Wellington region.
On the undercard, Lower Hutt's Gentiane 'AAA' Lupi (15-2) edged Natalia 'The Hun' Teller (10-12-2) via split decision in a women's 64kg bout, while Wairarapa's Zane 'Hybrid' Hopman, improved to 19-3 with a unanimous decision victory over Pati 'The Arsenal' Afoa (28-15-1) in a cruiserweight match.
Nick Taylor (19-5-1) handed Sean Redgrave (5-1) his first career loss with a punishing first-round knockout, while Nato Laauli (29-9) topped Thomas Peato (13-8) in a heavyweight bout.
