I've got a couple good sized limbs from a silver maple tree. Is this good bow stock?

the ones in my neighbors yard always break limbs off

no

Form what I've heard that would be one of the softer of the maples and thus not so good for bows. They are typically found near water in lowlands around my parts.  Cheers, Matt

You want to look for sugar(aka hard ) maple.

Edit: I see your form MI, have you tried to find Hop Hornbeam(iron wood) or Serviceberry(someplaces called saskatoon)? Those are among the best of native northern species of bow woods around .70 sg each.