The 43-year-old set marks in the women's aged 40 to 44 grade at the New Zealand Masters Games at the Forsyth Barr Stadium.
In the 2km she was timed at 7min 19.1sec and beat the old mark by 23 seconds.
In the 1km, her time of 3min 29sec was nine seconds faster than the previous best.
In the 500m, Howlett was just under a second faster than the old mark with her time of 1min 38.2sec.
As a teenager, she broke the New Zealand secondary schools junior discus record.
She competed in athletics on Sunday and won gold medals in the discus and shot put.
Howlett has been inspired by the support given her by members of the Port United Rowing Club and by her coach Ray Sinclair.
"I've found something that suits me," she said. "I've got more mental discipline now that I'm older and I'm training harder."
Other records were set by retired Southland sheep and beef farmer John Wilson (Riverton) in the men's aged 65 to 69 grade and George Venemore (80), of Auckland, in the men's aged 80 to 84 grades.
Wilson (66) took 15 seconds off the record in the 2km with his time of 6min 53.3sec and lowered the 1km record by nine seconds, to 3min 17.8sec.
He has been rowing on water for 45 years and won the New Zealand premier pairs title in 1967.
Venemore, who took up the sport last year, broke records in four disciplines. His 2km time of 8min 32.9sec broke the lightweight and heavyweight records in his age group. His record in the 1km is 4min 12.9sec, the 500m is 1min 56.5sec and the lightweight record in the 300m is now 1min 05.8sec.
Brian Hutchison (79), of Blenheim, was the oldest rower on the water at the Masters Games and won a bronze medal in the double sculls with his son Ross (51) and a gold medal in the quadruple sculls.
He won a gold medal in the 300m in indoor rowing in a time of 1min 07.3sec.
