it would probably be easier to describe any problems your having, Settings for about any fish finder will change with a number of  factors, water temps, water clarity, depth....I generally have to tweek things between trips just because the water changed...find a base setting you like and learn to tweek it a little to better match your conditions

when you turn on the fish ID (fishy symbols) are you seeing fish then?  if not then you probably have a bad transducer,,,if you are then it sounds more like contrast and brightness settings....are you seeing anykind of information about the bottom,,is the depth about right or nothing at all.  if your seeing lots of info just above the bottom and it dont look like arches, it could be that your sensitivity and chart speed and ping rate are all to high....start with everything in the middle and start adjustments from there till you get presentations that you like.

One other thing,,,every fish in the world is laying on the bottom this time of year,,,so you may have so many arches that it just looks like a dust storm from all the arches

Sounds like a bad transducer to me. I had the x15 unit and my dad had the same unit but hes wouldnt mark fish in deep water at all. Anything over 20 ft was out for arches. We still got a good bottom reading. your 17 unit is pretty close to the same unit as my 15. well we took both boats to the lake one day and i found a bunch of arches in deep water an dad couldnt mark them. I took his unit off and put it on my boat. It marked fine. He replaced his transducer and it fixed the problem. So if you have the transducer mounted right and i think thats your problem. His was still pinging like always just not marking fish arches. I will note he was bad to leave his unit on once he pulled the boat out of the water and also he let the grand kids play in his boat and it was left on....so he said. I dont know if thats what burnt it up or what but i think so. He also had sent his unit back several times and it came back operator error from lowrance...lol. I think the whole time it was the transducer. Its working fine now. i always run the ping speed and the chart speed on 100% with my unit. greyline is just for changing the color somewhat to get better detail. shouldnt have nothing to do with marking arches....just how dark or light i think.