Since it's not a proprietary Garmin transducer, have you talked to Airmar ?

Yes,  Airmar told me that the transducer is not a NMEA 2000 compatible transducer.

Hi Marcus,  I see some info about your transducer at West Marine...

https://www.westmarine.com/buy/garmin--airmar-b744v-thru-hull-multisensor-dual-frequency-transducer--13178439

...but I still can't tell if it outputs fishfinder style sonar data. If so, that can not be carried over a NMEA 2000 network.

But it may be possible to get numeric depth, temp and speed onto N2K using your YD bridge and an Actisense DST-2:

https://actisense.com/products/dst-2-nmea-0183-digital-transducer/  

Actisense should know if this is possible.

A transducer that connects to nmea2000 is something like this:

https://www.airmar.com/productdescription.html?id=110

Your B744V is designed to connect to a fishfinder.

@ben-ellison will check with Actisense that's a good idea. Maybe during the next haul-out I will replace the sensor, but this is a while away.

Marcus, did you solve this? 
can the airmar data from the fish finder garmin 400C  be connected to the nmea2000 network? 

Posted by: @pilotmarcus

Hi,

I would like to connect the Airmar B744V transducer to a NMEA 2000 backbone directly. The transducer can do depth, temp and speed. Currently it is hooked up to a Garmin Fishfinder 240 and then via a YD 0183/2000 converter to the backbone. I would like to get rid of the Fishfinder and also monitor the waterspeed. Garmin has an Adapter Kit ( https://buy.garmin.com/en-RE/ssa/p/68537), but i think it is discontinued and I can not find  specs.

thanks,

Marcus

I think you forgot about the adapter, which is a must when you connect the sensor.