fish finder doesnt show depth

I have a humminbird 160 fish finder that shows water temp correctly, but consistently shows a depth of 0.

I have heard that air pockets between the transducer and the surface it is mounted on can cause this.

i have the transducer placed on the inside hull, kept in place by duct clay and it seems solid.

Any ideas what could cause he fish finder to show 0 depth ?

It may be solidly in place, but if the transducer surface and that of the hull don't match, you could have an air space between them. This is certainly what it sounds like.

I have always mounted my transducers into a foam block that was gooped to the hull. Then I have a little tube that can be used to fill any space between transducer and hull. When filled it works perfectly. Occasionally I will go a few months and forget to add a little water down the tube and when that happens, the depth goes away.