Willetton adapted to the tough wet-weather conditions quickly, with captain Josh Coleman kicking the first goal in the opening minutes.
The lead was 13 points at half-time in the low-scoring match.
Scarborough were unable to convert a number of chances in the third quarter and Willetton kept extending their lead through accurate goal-kicking.
Brandon Ellis ended the match with four goals and Josh Kyle kicked three in a best-on-ground performance.
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The final score was Willetton 8.5 (53) to Scarborough 3.11 (29).
David Myors won his first premiership as coach and built on the successful history of the Willetton colts.