I bought a humminbird 798cisi nvb combo last summer and I am having problems with it.  The first problem which has been since it was brand new is that I can be fishing in 5 feet of water and all of a sudden the depth on the screen will just keep changing from 5 feet to 20 feet 2 feet 12 feet etc.and just go crazy.  I haven't figured that out yet and now today I have a new problem.  As soon as I turn the key to start the motor it loses power and then won't turn back on unless I unplug it and plug it back in.  This just started today.  Anyone else have any problems like these?  It's still under warranty so I might just send it back but don't want to if there is nothing wrong with it.  Thanks

 I got that problem when I added the Down Imaging in January. I have the 798ci SI also. A solution is in the process at Humminbird. If you registered your unit, you will get the corrective software in your account when it is available.

As far as the cutting off, your battery is not strong enough to keep at least 10V going to the unit when the engine is started. It may be just corrosion on the battery terminals causing resistance. It could be a too small, undercharged, or weak-from-age battery. That is a common occurrence also and is not a Humminbird defect-it is caused by your boat battery maintenance.

Thank you very much for your response.  How do you add down imaging and how do you register the unit?

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