Is this AC adapter compatible with Arris SBG8300?

I couldn’t find anything on the SBG8300 manuals for the power supply but I did see one that had a 12v 3amp power supply. If it was me, I’d return it as it doesn’t have a rated power supply. If it was a used purchase of ebay and there isn’t a return, you can always try it as you won’t hurt anything with a lower amperage (or higher for that matter). It might not be stable if its needing more than 2 amps and the supply can’t supply it.

Its the voltage that’s the concern.