After scoring 5.00 with his first wave, Hovell was always in front in the final, but he kept busy because Aarsen was snapping at his heels, having scored 4.85 on his second wave.
Both surfers recorded points on six waves in the final, and Hovell's two scoring waves were the fifth and sixth he surfed.
Aarsen's best wave, scoring 5.8, was also his last in the final.
Another Gisborne SUP surfer, Stella Smith, finished second in the open women's final, behind defending national champion Billie Scott.
Smith's two-wave total was 9.90 (4.50, 5.40) against Scott's 11.90 (7.50, 4.40).
Both Hovell and Smith are New Zealand representatives in SUP surfing.
Former Gisborne surfer and 1998 national champion Chris Malone (Raglan) was second in his over-35 quarterfinal and semifinal and will contest the final tomorrow.
However, after advancing second in his o40 quarterfinal, he was eliminated in the semifinal.
Tomorrow is finals day in the champs.