After the 2.30pm start at the lake, Wright emerged on his bike at Kaierau at 3.14pm with a reasonable lead over a chasing group of three, including Gemmell.
However, the two teenagers cut lone figures by the time they raced each other back up Devon Rd to the finish.
While Wright's time was only one minute and 45 seconds over the hour mark, the young man said his goal had been to win rather than break the 60-minute barrier, as Palmerston North's Jake Jackson-Grammer managed the year before.
"The heat wasn't too bad, I just had a really hard training week this week, my legs were dead for that bike and run.
"Luke was catching up, I had to dig deep to stay away from him."
Wright is preparing for the Under 19 Elite Nationals on March 7 and as he sat recovering on the rugby field sideline, the young man said the event pushed him harder than any training session could.
Gemmell, who is also preparing for the nationals in Gisborne, likewise got a lot out of the rivalry.
"I've never ever beaten James, I just wanted to see if I could catch him."
The teenager felt his swim had been strong, but was more pleased to have put in a good run to get close to Wright, who had won the U19 elite division at the January round of the Kiwi Tri Series in Takapuna.
Luke Gemmell wasn't the only family member to shine on Saturday as Rob Gemmell finished in a strong 1h 04m 32s time to be comfortable winner of the men's vintage section.
The first competitor back to the rugby clubrooms was short-course winner Rob Condor, who completed the smaller version of the long course in 53m 01s.
With major sporting events and music concerts at both ends of the North Island on Saturday, overall entry numbers for the triathlon were not high, with 49 individual competitors and nine teams combined across both the short and long-course events.
The event is held in conjunction with the Wanganui Multisport & Triathlon Club.
The club's next event will be the triathlon/multisport races on March 16 along the Whanganui River course.