First windless day in two weeks, so I get to the lake, unload the boat, park the truck. Start heading to my secret spot, turn on the humminbird 899, and it shut downs. Then reboots, then shutdowns... Realizing something's up, I go to the internet. I try moving the power supply to the trolling motor batteries, no luck. I start unplugging accessories, no changes. I remove the lake master chip and some other sd card I had in there, then finally gave up and headed in. I get home, connect the head unit straight to the battery, update the firmware, and it still constantly reboots. So it looks like I'm shipping it back to humminbird and spending $280 on a shoddy reconditioned unit. At this point, I have over $5,000 worth of accessories, and a minnkota I link, so switching brands isn't even an option.