I recently purchased a helix 7 and am still trying to figure it out...Saturday when I left the lake I turned it off like normal...that after noon I noticed it was locked up in shutdown mode...had to unplug it to turn it off..did the same thing Sunday....any ideas what's going on.

Typically that is a result of low power.

ok so check and clean battery connections?...would be great if that's all it is.

Exactly what is the unit power cord connected to?

my cranking battery....and it's been in the boat for 7 years...probably past time for another...what do you think about a duel purpose for cranking and electronics?

Do you have just the 6' unit power cord connected to the cranking battery, no other wires or connections involved?

The Sears PM-1 group 31 has been a good choice before they were discontinued.

At a minumum you need the MCA your outboard requires and then as much Reserve capacity as you can get to function like a deep cycle battery.

got everything but the trolling moter on it...haha

Do you have any SD cards in the unit? I had a similar issue recently and had to remove my SD card before start up and shut off. I have had that SD card in the slot for over 6 months without any prior issues as well.

I do but this started just before I installed it.

I had this same problem and still do every so often with a 798. It is surely a power issue. With my unit the head is not making a good enough connection with the power cord which plugs into the bottom of the unit. Make sure the head is pushed all the way down when you mount it. Also, Wayne P. gave me a tip on this forum some time ago. Take a pencil tip and very slightly move the connecting tips in the power head. Be very careful not to break them. Then plug the head back on. This seems to help with my 798 for awhile and then the problem returns.
Hope this helps you.