Re: Depth Sounder Replacement in a SM 2000

Bill Kinney

Transducers come in two flavors these days, "Smart" and analog.  

The "smart" transducers output digital NMEA2000 data directly and connect to the network backbone.  All of the smart transducers are identical with the possible exception of the connector they use on the drop cable. The only thing missing from the "smart" transducers is the sonar information is limited to depth ONLY.  You do not get any kind of "fishfinder" display, if that matters to you.  This limitation also applies to some of the "multi" transducers. The more "stuff" packaged into the thru-hull package, the smaller and less capable is the depth sensor.  For speed and temperature there is no functional difference at the instrument between the "smart" and analog versions.

The analog transducers are also pretty much all the same, but each brand uses a different connection. In this case, they connect to some smart device in the system, usually the MFD, or sometimes a separate sounder module, which then processes the data and outputs it on the NMEA2000 network.  Almost all are made by Airmar, differing only in what connector they put on the end of the wires to match the final brand seller. (Raymarine, Garmin, B&G, Simrad, etc.)

We installed Airmar's ultrasonic speed sensor UDST800 a few years ago, and it worked great--until it didn't.  At that price point the failure was painful, and we went back to cleaning a paddlewheel. To put things in perspective, the 800 series ultrasonic speed sensor was vaporware for YEARS in the Airmar catalog before it was actually available on the market, so I wouldn't hold my breath for the 900 to actually be a physical product in the real world anytime soon.

If you have a compatible sounder module, or MFD, you can actually use an in-hull transducer, like the Airmar p-79, avoiding another hole in the hull.  No speed or temperature of course, but it works well as a sounder.

Bill Kinney
SM160, Harmonie
Hollywood FL, USA

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