Fishfinder problem

[JeffHaught]

Hello all, Here is my problem. I have a 16ft aluminum Gruman. I use a trolling battey to power my trolling motor as well as my fishfinder. Latley when I turn on my trolling motor the fishfinders screen dims to where I can hardly see it. Is there something I can do to correct this or do I need to get two separate batteries? Any help would be appreciated. Thanks,
Jeff

[misfit]

the only time i've experienced that is when the battery needs charged.once it's discharged so far,the draw from the motor will cause the ff screen to flicker or go completely blank.check battery charge and connections.

[Hetfieldinn]

Why not use the cranking battery for your main motor to power your fishfinder? (I'm taking for granted that you have a main motor to power your 16 foot boat)