I have a Lowrance HDS-7 and it seems that when I power the unit down it powers itself up after a few minutes. Any insight?
Make sure it is completely powering down and you are not just dimming the brightness.
Are you powering off by holding down the power button until shutdown, or are you choosing power off from the popup menu and pressing ENT. Go with pressing ENT on the power off option. If you are completly powering it down for sure, there is probably a malfunction and you'll need to get it taken care of.
Unplug the power cable, and then plug it back in...does the HDS-7 turn on by itself now? If yes, there is a probably short in the keypad, likely due to water intrusion. You'll need to contact Lowrance support at 800-324-1356 or you can email them by going to http://www.lowrance.com/en/Support/Product-Support/Contact/ to get it taken care of.
Give them your serial number and name and address and phone number in the email to hopefully speed up the process.