Thank you, Peregrinus! Just the kind of info I was looking for. According to my electronics guys, that DST800 has a history of malfunction. They've quit using them.
I had an EchoPilot forward scan that only gave a narrow width sounding straight in front of the boat about a boat length ahead that was difficult to interpret at times. To find a channel I had to turn the boat back and forth, and was never really confident in what I was seeing. I'm waiting for the next generation that gives a picture of the bottom 30degrees wide. Right now they're very expensive and require two transducers 18 inches apart...I don't really want to put two more holes in the boat.
S/V Kristy SM243