He jumped from the outside of the second row to pass Wayne Russell for the lead at Hell Corner and would not be headed thereafter.
Beric Lynton passed Russell at The Chase on Lap 1 as Sherrin gapped the field by more than two seconds in the #27 BMW M4.
Lynton rapidly caught up to the leader once he cleared the #58 BMW M3 but could not fashion a pass.
He very nearly lost the rear of the #23 BMW M3 completely while turning off Skyline on Lap 4 and straight-lined The Esses, as the margin grew again.
Sherrin was at one point back to 2.5s up before taking the chequered flag 1.8944s to the good, with Lynton second and Russell more than 28 seconds further back in third.
Anthony Soole (#4 BMW M4) made it an all-Class X top four, with Jimmy Vernon (#50 Mitsubishi Evo) winning Class A1 in fifth outright.
Simon Hodges, who started from first position and initially slotted into fourth, would not be classified a finisher after technical dramas for the #31 BMW M4 in which Jayden Ojeda took victory in Race 1 of the weekend.
Race 4 starts tomorrow at 08:05 local time/AEDT.