Thru Hull transducer for Garmin 178C

I installed a new GPS/fish finder in my Hobie Outback, everything is working great except the transducer is not reading thru the hull. I install it using a foam cut out to set the transducer in. The cut out is seal to the hull with marine goop. Then I filled the center of the cutout with clear vaseline. Set the transducer into the vaseline and set it down to remove any air bubles or voids between the transducer and the hull. However when I tested it in water I did not obtain a depth reading or fish location. The GPS device is working outstanding. I have used this process before installing tranducers in fiberglass bass boats and everything operated properly. Question is the keel on the OutBack solid poly material or is it hollow between the hull and keel. If it is hollow or solid thick ploy keel this would be the reason for non depth/fish reading. Does about the keel structure. I do know my transducer is operating proper I test in water.

Thank you

You might be better off if you mount the transducer permanently to inside of your hull. If there is a gap between the transducer and the hull, or the transducer is moving around, you probably won't get an accurate reading.

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Waterman at Work - Kayak Fishing Photos, Video,Kayak Rigging - Blog

Don't have an answer to the question but if you are certain all the voids and bubbles aren't the issue and that the transducer is working, it would have to be an issue of the keel. Nothing left. Consider moving it. I used the method you describe in a power boat in the 70's, worked fine. I used water inside the "cup". Easy to do as I set the transducer in the "drain hole area" of the hull and would pour a pail of water in the bottom of the boat. Worked flawlessly. It was the only place it would work though because of hull thickness and double hull/ply everywhere else. I still use that method today if using a depth finder. Make a little deeper well. Use water. Can even plug the top if it's an issue. There are plastic tubes, glasses, buckets, all sorts of things to use. Good luck.

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Yakkingaway
Portsmouth, VA