I agree w/ Okuma on maxing sensitivity for jigging, also check ping speed - you want to crank that up pretty good too. Another thing that could be a factor is where on the boat you are making your drops from w/ respect to the location of the transducer.Also, remember that if the boat is drifting a fair amount, fish marks will look like smeared lines, and the jig drop can take on an unusual look, especially if your drop rate is on the slow side.