Defender has been very responsive and helped me with troubleshooting advice, as well as offering to coordinate communications with Lowrance. I did talk to Lowrance directly, and after going through their standard troubleshooting which included trying two resets to factory defaults, I got bumped up to a senior tech guy. In the end he seemed pretty stumped as to what the issue might be. The transducer seems to have crapped out (you can't feel any clicks when you touch the transducer) but he didn't seem convinced that is the only issue. (For example, under the Sonar menu the only sonar listed is labeled "invalid.") Bottom line, a new transducer might or might not solve the problem.

I'm going to order one of the Zeus units (thanks Larry) and a new transducer. I'll be home for a wedding in a few weeks and can't afford not to have things working well this summer. I do have a spare depth sounder (part of the original instrumentation that came with the boat) but the depth occasionally gets temperamental.

Thanks again Stephan and crew, what a great company. And I'm so glad for your heads up here, Larry on the Zeus.

Max