Re: lowrance 26
I agree with JB. I would turn the sensitivity up to the point you are picking up a lot of false returns or noise first. If the sensitivy is too low you will not see the fish when he is in the outer edges of the cone. In this case you will not see the fish unless right under the transdicer and it will not make much arch at all.
Now if you only see the first part of the arch the transducer may be pointed forward. If your only see the back part of the arch the transducer may be pointed too far back.
Also a transducer with a narrow cone like the 8 degree I use for deep salt water will not show much of an arch in shallow water.