Kayak anglers have long debated whether the Lowrance DownScan Imaging (DSI) or the Humminbird Down Imaging (DI) can be used in a shoot through kayak hull application. Some sources on the internet have even suggested that the manufacturers do not recommend it. KFM went directly to the sources, engaging directly with Lowrance and Humminbird, to get to the bottom of the rumors. The bottom line is that YES, you can use DSI/DI in a through kayak hull application, however, there will be a minor performance loss.

Lucus Steward, Product Manager at Navico (Lowrance parent company) had this to say:

We certainly do endorse shooting DSI through a kayak hull. I have had great success using Marine Goop. There is a small loss in coverage.

Lucas went on to provide some real images to demonstrate the effects. For 800 KHz, side to side (across track) beam width is cut in half when mounted as a shoot through kayak hull. This reduces the amount of coverage you have. The signal is also attenuated significantly. Small targets and thermoclines do not show up. Max depth is also greatly reduced. In the following picture, the right set of images are shoot through kayak hull. The top images are in 35' of water and the bottom images are in 75' of water.

For 455 KHz, side to side (across track) beam width is cut in half when mounted as a shoot through kayak hull. This reduces the amount of coverage you have. The signal is attenuated slightly. Small targets and thermoclines show up better at 455KHz than at 800KHz as shoot through kayak hull. In the following picture, the right set of images are shoot through kayak hull. The top images are in 35' of water and the bottom images are in 75' of water.

Mark Gibson, the Director of Research and Development at Humminbird, had this to say:

As with any installation inside the hull, there is some loss of signal versus having it mounted directly in the water; however, the amount of loss on the DI due to being mounted in the hull of a kayak using the kit we provide is not very much, and can be easily compensated for by increasing the sensitivity. I ran out yesterday on a kayak in between rain storms, and quickly installed the DI transducer in less than a minute and took these snapshots. You can see the difference, but I didn't try to compensate for sensitivity, so the sensitivity setting is the same for both shots. The shots on the right are from the installation inside the hull. The shots on the left side are from the transducer being directly in the water.

So there you have it. You can indeed use DSI/DI in a shoot through kayak hull application!