I have a plug knocker that's about 40 some years old, and has saved many a crank (single pole casting/trolling) :

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.... but, I wouldn't expect it to work with a 2oz trolling weight (torpedo shaped). Now .... were I "Pulling" cranks (no added weights), then it might be effective. But, I'd still probably reel in all the other cranks before trying to free the snagged one.