I have an old Raymarine ST60 Tridata instrument, with a non-retractable Airmar 2″ through-hull depth transducer (assumedly M78713) and a retractable 2″ speed transducer (assumedly M78712), probably also from Airmar.

Now, of course just after lowering, the Tridata surprised me by displaying a depth of ----
m, which is a sounder, wiring, or instrument error. The wires showed some voltage, but the sounder wasn’t ticking.
Swapping the cable didn’t help, swapping the instrument was expensive—used ST60’s go for 200+ € on eBay—and swapping the transducer would have come at the cost of lifting/lowering.
The good news for everybody out there who wonders: yes, a brand new Airmar DST810 (and also the Airmar DST800) does fit the 2″ housing of the ST60 / M28712 speed transducer! You only must swap the yellow o-ring (for sealing the new valve housings) with the provided black o-ring (for legacy housings)!
Swapping the transducer seems like scary business, but isn’t as bad as it sounds…
Now the ST60 can’t display the depth/speed information any more (it only features the outdated SeaTalk). Long term I’ll replace it with a B&G Triton², but due to the global supply shortage, those are currently unavailable. However, I connected the DST810 to my chart plotter via NMEA2000, which does the job for now.

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