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Installing the Eyes: Garmin GT51M-TH Thru-Hull Transducer
Drilling a hole in the bottom of your boat is always nerve-wracking. We walk you through the precision installation of a thru-hull transducer to unlock CHIRP ClearVü and SideVü sonar.
Why Thru-Hull?
For a high-performance hull like the Contender 31, transom-mount transducers often lose bottom reading at high speeds due to turbulence (aerated water) coming off the steps. A Thru-Hull Transducer like the Garmin GT51M-TH sits in "clean" water forward of the props, ensuring solid depth readings even when running 40+ MPH.
The Installation Process
1. Cutting the Fairing Block
The Contender 31 has a steep 24.5-degree deadrise. If you mount the transducer flat against the hull, it will shoot sideways, not down. We had to cut the included high-speed fairing block to match this specific angle. This ensures the transducer face is parallel to the waterline while the top matches the hull's slope.
2. Drilling and Sealing
After double-checking measurements (and checking inside the bilge for obstacles!), we drilled the hole. The critical step here is sealing. We used marine-grade sealant (3M 5200) to coat the fairing block, the hull surface, and the stem of the transducer. The goal is to create a monolithic bond that will never leak, even under the stress of offshore pounding.
3. Cable Routing
Fishing the thick transducer cable up to the console required navigating the rigging tubes. We used a fish tape and plenty of cable lube to pull the connector through without damaging the delicate pins.
