My hds8 on the bow will work for about 15 mins then it will start flickering and goes to the lowrance home screen. I have to unplug the power, plug it back up then another 15 min later the same thing.

What generation is it? Does it have the latest software update?

It is gen1

Clean all your connectors and verify that you have good voltage to the head unit. Can you move it to the console position and see if it works there?

I just updated it the other night. I will see if that works .if not I will move it to the driver console and see if it still gives me problems

You might try a soft reset.

After the update it still does it. It is flickering after being on the lake for a bit with livewell pumps on and both fish finders going. I think the battery reserved volts are dropping.

Do you have it hard wired to the battery or to the power supply in the front ?

Bingo! The factory wiring is subpar and you will need to wire your graphs directly to the battery, the livewell comment was all you needed to say.

Yes it is wired to the front power supply

Run wires to the battery and your problems will go away.

You can display and/or alarm for voltage readout on your HDS screen. That way you can monitor your voltage to the HDS.
NEVER connect your electronics to your trolling motor batteries and always wire them directly to your cranking battery.
I recommend a strait direct wire with nothing else connected, to the cranking battery.