I've recently installed a DST810 to replace a failed, aging depth sounder transducer, and to gain speed and temp on my N2K network. Depth works a treat for me, unlike other DST 810 depth error posts here.

Here's my weird bit:

• My DST810 speed through the water in knots reads really high as compared to the GPS SOG in knots. Like a bit more than twice the value. And I'm not running rapids in my 8' draft sailboat!
• When I change the units on my DST810 to m/s, the resulting speed through the water value is very close to the GPS SOG in knots, and matches my Mk1 human eyeball estimate of speed through the water in knots.

I can't just leave it set to m/s setting, as that just offends me. And I'm easily offended <grin>.

I'm working with Airmar tech support, who are both very supportive and very responsive. No resolution yet, but I'm hopeful, and will report back when resolved.