In a Bellerive Oval fixture restricted by rain to a maximum of 44 overs each, WA posted 9-248 with Sam Fanning top-scoring with 66 from 91 balls.
The Tigers, set 252 runs to win under the Duckworth-Lewis system, lost six wickets and reached their target from 38 overs to win Monday's contest with 36 balls to spare.
Silk dominated with 81 from 75 deliveries, scoring his 2000th domestic one-day run in the process of Tasmania banking a fourth win from as many outings in the Dean Jones Trophy.
Silk, who struck nine fours and a six, and a batch of experienced teammates were untroubled in the run chase. He combined with fellow veteran Matthew Wade (46 not out from 43 balls) in a defining 104-run partnership for the fifth wicket.
Opener Caleb Jewell set the Tasmanian tone with an aggressive 48 from 37 balls featuring seven fours, and evergreen Ben McDermott made 42 from 49 deliveries.
The quartet overpowered WA's bowling attack with paceman Mahli Beardman (2-55 from seven overs) the sole multiple wicket-taker.
Earlier, WA opener Fanning's composed knock and an aggressive 56 from 51 balls from one-day debutant Teague Wylie underpinned the visitor's total.
Fanning and fellow opener Joel Curtis (22 from 23 balls) put on 50 runs in eight overs amid early rain interruptions.
Curtis, stalwart Cameron Bancroft (12 from 19) and Sam Whiteman (14 from 15) all failed to capitalise on promising starts and when Fanning fell in the 29th over, the visitors were 4-147.
Allrounders Hilton Cartwright (15 from 15) and Ashton Agar (23 from 22) were both dismissed in the following 10 overs as Wylie launched at Tasmania's bowlers.
The 21-year-old struck four fours and a six before edging to wicketkeeper Ben McDermott from the bowling of Brad Hope, who impressed with 3-40 from seven overs.
Paceman Billy Stanlake took 2-68 from nine overs while Iain Carlisle (1-22 from five), Nikhil Chaudhary (1-35 from eight) and first-gamer Ruwantha Kellapotha (1-41 from seven) also took wickets.
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