I was wondering if this compatible with my Garmin GPSMAP 943 xsv with a garmin gt51m-tm transducer a

Yes this is compatible with all of those items. You will most likely need a GMS10 network expander if you do not already have one. That can be found here, https://www.boemarine.com/garmin-gms-10-network-port-expander.html.