Can a transom mount transducer be mounted like an in-hull transducer?
Due to having a boat that is incompatible with a transom mount transducer, it may be desirable to install a transom mount transducer inside of the hull, sometimes called a shoot-thru-the-hull installation. If the boat is made of solid fiberglass, it is possible to install a transom mount transducer inside of the hull. When using a 500W transducer, the fiberglass hull can be no thicker than 5/8 inch. When using a 1kW (1000W) transducer, the fiberglass hull can be no thicker than 1 inch.
The following factors should be considered when installing the transducer in the hull:
- The hull must be composed of solid fiberglass without air bubbles, laminates, fillers, or dead air space
- The location must be in an area of clean (non-turbulent) water at all speeds
- The location must not be over any strakes or behind any obstruction on the hull that would create turbulence
Many modern hulls have a dedicated pocket for an in-hull transducer installation. Check with the hull manufacturer to see if your boat includes this pocket.
To test a location for in-hull installation:
- Fabricate a test cylinder from a section of PVC pipe or can large enough to contain the transducer
- If no PVC pipe or can is available, a plastic bag filled with water can also be used
- Temporarily seal the test cylinder to the hull with caulking or RTV sealer, and fill the test device with water or light mineral oil
- Place the transducer in the liquid, pointed directly toward the bottom, and weighted down to ensure the most accurate test results
- Using the attached Garmin fish finder/sounder, verify that the transducer is reading depths. Be sure to test at different depths and speeds, to ensure that the transducer is working properly
- If the sonar performance is significantly degraded, select and test another location
To permanently install the transducer:
- Lightly sand the surface of the hull and the face of the transducer with 400-grit wet or dry sandpaper
- Build a dam using strip caulk about 1/4 inch tall
- Pour about 1/8 inch of two-part, slow-cure epoxy into the dam
- Place the transducer into the epoxy, turning the transducer to work out any air bubbles
- Weight the transducer in place, and allow it to cure for 24 hours