Through Hull Transducer issues potentially?

[Scott K]

I have a buddy who installed a Humminbird fish finder in his boat last Summer. It has a through the hull transducer that he installed himself. I went out fishing with him a few times and sometimes the finder would work great and other times it would show like 1 foot or something like that (very shallow). I'm thinking it's transducer related - perhaps more material needs to be removed, or ? Thoughts

 

[Cuba Libre]

Has he got the transducer in a sealed oil bath? If not..much better performance if he does that. check out http://www.echopilot.com/user/image/fittingadepthlogtransducer.pdf

 

[spring fever]

I think CL has the right idea. X2

 

[Hookin'up]

is it a shoot through or a thru hull(drilled hole) I have same kinda issues when my HDS loses bottom but only when set to a depth shallower then bottom,
if it happens I set it to a depth 100-200 feet deeper then actual and problem dissapears