[Gerry Zagorski]

Not familiar with your particular unit but try this.....

Turn of all automatic settings and adjust manually....

First set your range to at least twice the depth of the water you are in.... So if you are in 20 feet of water set your range for 40 or more.

Now you want to do is adjust your gain so that you mark the bottom with a good solid reading and you should have a 2nd bottom mark or return at twice that depth which is a bit more faint but noticeable... In the example above, a good solid mark at 20 and a faint but noticeable mark at 40.

Now you know your gain is set so switch back the range to 20 or so feet so you are not seeing the 2nd bottom return.

If there are fish under the boat you should be marking them.... If no fish then try a larger sinker and see if you can mark it.