Probably, or possibly. Your boat's electrical system
is only a nominal 12 volts, it will range from 10.5 with discharged batteries to a typical 12.2 or higher and 14.4 when the alternator
is running. IF the Linksys can operate properly under that whole range, sure.
Odds are there's enough tolerance in it to do this, but a "buck boost" dc-to-dc converter, or a simple regulator
, that provides a regulated 12V for the router would be safer.