Transducers shooting thru hull?

I've been troubleshooting my Humminbird and ran across an article from Humminbird where they state they DO NOT recommend mounting side-imaging or down-imaging transducers in hull.  They were talking about shooting through a fiberglass or Kevlar hull, but now I'm curious.

It's not at all odd advice for a side-scan transducer, but down-imaging, too?

Has anyone seen a problem with the signal with a transducer mounted inside the hull?  I hadn't with Lowrance trasducers, but this Humminbird of mine has been a bit of a PITA for getting the settings right since the day it walked in the door.

Oddly, until recently Humminbird sold an in-hull mounting kit for kayaks (it's what I use).  Seems contradictory.

As an aside, I run a Hummingbird side finder on my power boat in saltwater and gave up using the side-view to search for schools of salmon. I wasted a lot of gas chasing "fish" that I finally realized were huge jellyfish and bull kelp strands and other detritus floating in the water column. I run two transducers, one on the transom for side viewing and slow trolling and the other is inside my 1/2" thick fiberglass hull just stuck on with silicone sealant for my fast running. Both mounts seem to show identical imagery when flipping back and forth between them.

The "down view" feature on my Garmin on the kayak uses the higher frequencies to provide the higher resolution details of structures, weeds, submerged trees and such but isn't worth a hoot for seeing fish. Perhaps Hummingbird feels the higher frequencies for down view resolution may be somewhat absorbed in the hull in both signal directions which could reduce the quality of the signal and image...in their mind.

I use the down view in lakes when trying to keep my offering above the top of the weed beds but in saltwater it has little value.

For the Hobies with the Lowrance-ready transducer mount, the signal must pass through the plastic cover plate in both directions so that would not be much different that shooting through the hull from inside.

Thanks!  The "no fish" problem happens in sonar and down-imaging, both.  I rarely use down-imaging - it's too new fangled for me think I know what I'm seeing (or to spend much time playing around with it).

I tend to agree with you that plastic shouldn't be an issue.  I'll let everyone know what Humminbird has to say when they're back at work.

I appreciate the feedback.

I've used down imaging thru hull with no issues.

Oh no!  I've been thinking the unit might be a lemon and it's sounding more and more like that could be the problem.  Fingers crossed it's the transducer.

Thank you.  Every tidbit will help when I call them.

I've used down imaging thru hull with no issues.

When you installed the transducer did you make sure to leave a little space between the transducer and the plate?  You want a little water to get in there so the transducer should not be lying on the plate.

Kevin

Thanks for asking.  Yes I did, but according to Humminbird (when I called them) that's not necessary as long as there's no air between the transducer and the hull.  I doesn't hurt to keep water beneath the transducer although the technician opined that it could possibly make temperature readings off.

When you installed the transducer did you make sure to leave a little space between the transducer and the plate?  You want a little water to get in there so the transducer should not be lying on the plate.
Kevin

Thanks for asking.  Yes I did, but according to Humminbird (when I called them) that's not necessary as long as there's no air between the transducer and the hull.  I doesn't hurt to keep water beneath the transducer although the technician opined that it could possibly make temperature readings off.

The transducer pocket in my Hobie provides great performance for my fish finder, it protects my transducer, and it was real easy to mount the transducer on the kayak.  The only problem I've had is that sand or mud can get in the pocket and pile up on top of the pocket's cover plate, between the transducer and the cover plate, which interferes with the performance of the fish finder.  To prevent this problem from developing, I hose out my transducer pocket periodically.  It's easier to hose sand and mud out of the transducer pocket if there's a bit of a gap between the transducer and the top of the cover plate, so I recommend that you leave some space between the transducer and the plate when you mount the transducer.

Yep, Hobie's transducer pocket was quite the innovation at the time.  Not enough for me to keep my Hobie, 'though.

There's a transducer pocket on my Trident, but my Humminbird transducer doesn't fit in it.  Oddly enough, Johnson Outdoors makes both Ocean Kayaks and Humminbird fish finders... I reckon someone must have been asleep at their desk the day they approved that change.