Kaiarahi Toa's time of 2 minutes 2.70 seconds was 1.89s faster than a Haeata Ocean Sports crew.
Another Horouta crew, Manu's GnT Angels, were fourth.
Earlier, Horouta's Manawahine won the junior 19 women's W12 500 final.
Medal success also went to Horouta's Tornado Sirens, who were third in the J19 men's final.
One of the closest races of the day was in the senior master (50 to 59) women's W12 500m.
Tuhono Tairawhiti, a combined Horouta/Mareikura team representing Te Uranga o Te Ra, finished fourth in 2:23.18, just 0.11 of a second behind the third-placed Auckland regional team, who were 0.45 of a second behind the runners-up from Portage Crossing.
A team from Ruamata had cleared out to win by over six seconds, but the next four waka could hardly be separated as they raced up the course.
At the finish line, the fifth-placed waka crew were only 2.41 seconds behind the runners-up.
The champs come to a climactic end today with medal races in W6 500, 1000 and 1500 distances.
The programme featured a few semis this morning, then it was into finals from J16 to golden masters age groups, building up to the glamour premier men's and women's W6 500 finals.
The regatta ends with J19 and premier men's and women's W1 250m dash races.
Several Gisborne paddlers are involved, including premier women's W1 500 champion Akayshia Williams and master men's W1 500 champion Bruce Campbell.
Results of other W12 500 finals from yesterday —
Master women: Mareikura Manawa (Mareikura) 5th.
Premier men's regional: Te Uranga o Te Ra 5th.
Premier women's regional: Te Uranga o Te Ra 4th.
' In early finals today, Horouta's Hinewaiariki crew picked up silver in the golden master women's W6 1000 and clubmates Hineteuru were third.
Horouta's Kaiarahi Toa were second in the master women's W6 1000 final with Horouta GnT sixth.
Horouta's Voltron were sixth in the master men's W6 1000.
Gisborne club Mareikura's Mareikura Manawa were sixth in the senior master women's W6 1000.
Gisborne paddler Vicki Flavell was in the Waitakere crew who won the master 70 women's W6 500 with a turn.