I have a HDS 7 without DI or SI. Its one of the first made models, not gen 2. Xpress boat with transducer mounted on outside of hull , back of boat. I need help on setting the sonar viewing. It seems to be blochy or cloudy. It used to have a very nice picture with arches and streaky lines that was easy to tell brush piles or fish or whatever, now I can't hardly tell what I'm looking at. I've adjusted it every way possible, got settings advice from lowrance but still a bad picture. Help please!