Crawford, winner of the event in 2009, was lying third after the swim but fell back to fifth on the bike - 2:35.45 for the 90-kilometre ride - which she acknowledges is not her strongest suit.
"The bike was below par - the other girls seemed to have that extra oomph," she said.
"But I had a really good run - my best ever time of 1 hour 23 minutes for the half-marathon."
Crawford ran 1:28 for the 21km at December's half-ironman, so a five-minute improvement was pleasing.
However, her target was a podium finish and she felt that would have been within her grasp over the full ironman distance.
There was the consolation of world ranking points in her bid to make the top 30 and compete at the world championships in Hawaii. Kessler led from start to finish, with strong-finishing Aussie Kate Bevilaqua second and seven-time champion Jo Lawn third.
The men's race was won by Belgium's Marino Vanhoenacker, the world's fastest ironman athlete.
The 35-year-old Vanhoenacker had to claw back a 50-second deficit late in the race to run down Australian Tim Reed, with 10-time Ironman New Zealand champion Cameron Brown a close third.
Kellogg's Nutri-Grain Ironman New Zealand (1.9km swim, 90km bike 21km run):
Men: Marino Vanhoenaker (Belgium) 3:55.03, 1; Tim Reed (Australia) 3:55.51, 2; Cameron Brown (New Zealand) 3:56.38, 3; Romain Guillaume (France) 3:58.03, 4; Aaron Farlow (Australia) 3:58.57, 5; Marko Albert (Estonia) 4:00.43, 6; Terenzo Bozzone (New Zealand) 4:01.51, 7; Guy Crawford (New Zealand) 4:03.29, 8; Jamie Whyte (New Zealand) 4:12.05, 9; Shanon Stallard (New Zealand) 4:14.46, 10.
Women: Meredith Kessler (US) 4:22.46, 1; Kate Bevilaqua (Australia) 4:30.37, 2; Joanna Lawn (New Zealand) 4:30.40, 3; Jessica Jacobs (US) 4:31.46, 4; Gina Crawford (New Zealand) 4:32.45, 5; Hilary Wicks (New Zealand) 4:32.51, 6; Belinda Harper (New Zealand) 4:37.49, 7; Anna Ross (New Zealand) 4:39.47, 8; Susie Wood (New Zealand) 4:41.33, 9; Candice Hammond (New Zealand) 4:43.25, 10.