Betcha it 'll work if the settings are right.....
First off take out of 'automatic" mode if it is......the automatic mode doesn't work worth a crap in salt.
Set the sensitivity about 86%.........usually if it's higher than that in the chuck they start to act up.
Over 200ft use 83 hertz or 50, depending on which yours is...
There's a setting for "noise"....sometimes this helps when it's on, sometimes it messes you up. If it is on keep it at "low".
In the "setup" mode......does yours come with depth options like 'Fresh', Shallow, 'Deep' etc ?.....if it does, leave it on deep all the time.
Ping speed....I find that certain ping-speed settings can mess a finder up.......I just have mine in the "normal" range...when I set it to high that's when it acts up.
I don't have the same sounder as you but I had all the same problems.....
I found that the place and height of the transducer makes a world of difference. In relation to waterflow over the transducer.......a difference of even as small as 1/2 inch in height can produce different results....too high and it messes up, too low and it messes up.
Try not to mount it where roiled turbulent water comes off the bottom of the transom........that causes more problems than electrical interference. I don't get electrical problems and my transducer is less than 1 and 1/2 feet away from engine leg.
Once I had mine (not your model) dialed in it will read down to 900 ft.......as advertised. Before I set it manually it wouldn't go 200.