Depth Finder cutting off.

When I crank up my boat motor my depth finder goes out. I have to turn it back on when I crank motor. What could be causing this?

If your df is connected to a weak battery it will cause it to keep cutting off. I had mine connected to my trolling batteries and late in the day (after all day trolling) my df would start cutting off. Wasnt long before the batts died and the tm quit too. Maybe the battery youre connected to is taking most all it's juice to crank the motor. (merely guessing) Try another battery.

Thanks, I wanted to confirm that. The batteries in my boat are 5 years old.