Read more: Crosby's absence in race stirs plenty of interest in top job
While others struggled on Saturday's bumpy track, Marsh took the approach of using speed to drive through the ruts.
He said racing against some of the country's best at the New Zealand Championships in January gave him confidence.
"Racing against (New Zealand champion Jonathan) Allard and all those top guys and seeing them wide open in the New Zealands showed me that it can be done."
Allard and local driver Colin Entwisle are among the drivers who have helped Marsh, but he also had praise for those closer to home,
"If it wasn't for mum and dad, I wouldn't be racing and the crew have put in a lot of hard work getting the car right."
Marsh last won a race while in the youth ministock class. This is his third season in the sprint car ranks, his second in a KPC chassis.
"It was good to get a taste of (victory) again."
Read more: Warning issued as Bay beach closes after sewage overflows into ocean
Marsh won't be travelling to the North Island Sprint Car Championship at Palmerston North next weekend, but having proved to himself he can run at the front of the field, he wants to stay up there.
The sprint car feature was won by former national champion Rodney Wood, who also won the first heat. Wood's son Cole won the first heat and feature in the six-shooter class with Gisborne's Chris Mackey winning the second heat.
Also from Gisborne, recently crowned national saloon car champion Dan Corrin looked set to continue his recent run of victories at Baypark winning both the heats. But a bad start in the feature left him with too much to do to catch winner Steve Cowling.
There was a first win for stock car driver Karl Warner in the second heat, with Matt Nielsen winning the first and Hamish Curd the feature.
Luke McClymont won three of the four youth ministock races, including the feature, with Ricky Gladding taking the other.
Street stocks took to the Baypark track for the first time for many years, with Ben McArthur taking the feature win.