He followed up with a ninth and 15th place and was seventh overall for the day.
"I had an absolute blast," Townley said.
"I really like sand tracks, it got tougher and tougher out there, but overall I really enjoyed it.
"My overall race speed in Moto 1 surprised me - I hadn't raced in a crowd like that for a long time."
In race two Townley ran in the top six early on but his lack of race fitness told and he fell back to finish ninth.
"The final moto was going well but on lap three or four I dropped it in a corner and I was spent," said Townley.
Townley will continue in the substitute role with the Penrite Oils Honda team this weekend at the Manjimup 15,000 invitation event in West Australia.
It was a tough weekend at Wanneroo for Suzuki racer Rhys Carter (Mt Maunganui) who failed to finish the opening moto and then posted a seventh and 13th for 17th place overall. Carter has slipped one place in the Pro Open standings and is now eighth at the halfway point of the series.
Scotland's Billy MacKenzie (Yamaha) - the runner-up to Cooper in the 2014 NZ title - won the Wanneroo event with a first, second and fourth. Defending champion Matt Moss (Suzuki) was second and extended his series lead over KTM rider Kirk Gibbs to 22 points.