Upgrade your boating experience with the Garmin GT21-TM transom mount transducer, a powerhouse for serious anglers chasing fish in coastal waters or pushing offshore. This versatile unit combines high-performance traditional sonar with advanced ClearVü CHIRP scanning technology, delivering razor-sharp images of fish arches, bottom structure, and underwater terrain. Whether you’re targeting trophy bass in shallow bays or scanning deep reefs for snapper, it paints a vivid picture beneath your hull, helping you locate and land more fish with confidence.
Built tough for real-world marine conditions, the GT21-TM mounts easily on your transom and integrates seamlessly with compatible Garmin chartplotters and fishfinders. Its fast-response temperature sensor keeps you informed on water conditions, letting you adjust tactics on the fly as surface temps shift with tides or weather.
Standout Features That Deliver Results
Dual Sonar Powerhouse: Traditional CHIRP at 50/200 kHz (600W) for exceptional target separation and fish ID, paired with ClearVü CHIRP at 260/455 kHz (500W) for nearly photographic down and side views of structure.
Deep Water Capability: Reach up to 1,500 feet with traditional sonar and 1,000 feet with ClearVü, ideal for everything from inshore flats to offshore canyons.
Wide Coverage Beams: Traditional 40°/10° beamwidth captures broad areas efficiently; ClearVü offers precise 2.0° x 51° at 260 kHz and 1.4° x 29° at 455 kHz for detailed scans without losing bottom contact.
Rugged Transom Design: Handles 0° to 70° deadrise/transom angles, with a 30-foot cable for flexible routing on most boats.
Plug-and-Play 8-Pin Connection: Simplifies setup on Garmin marine displays, including GPSMAP, ECHO MAP, and STRIKER series.
Detailed Specifications at a Glance
Category
Traditional Sonar
ClearVü CHIRP
Frequency
50/200 kHz
260 kHz (245-275 kHz) & 455 kHz (445-465 kHz)
Power
600 W
500 W
Beamwidth
40°/10°
2.0° x 51° @ 260 kHz / 1.4° x 29° @ 455 kHz
Max Depth
1,500 ft
1,000 ft
General Specs
Details
Sensors
Depth & Temperature
Pin Count
8-pin
Cable Length
30 ft
Transom Angle
0° to 70°
Why Anglers Swear by the GT21-TM
In the heat of a tournament or during a family fishing trip, clarity is king. Traditional sonar excels at marking schools of baitfish and gamefish with crisp arches, while ClearVü reveals hidden wrecks, drop-offs, and brush piles like a downward-facing spotlight. This combo reduces guesswork—spot a thermocline, track bait balls, or pinpoint that submerged log where lunkers lurk.
Perfect for bass boats, center consoles, and offshore rigs. Users report fewer missed strikes thanks to superior separation, even in murky water or heavy cover. The built-in temp sensor helps dial in lure choices, as species migrate with subtle changes.
Effortless Installation and Pro Tips
Mounting is straightforward on most hulls: Clean the transom, select a spot 1/3 from the keel to stern, and secure with included hardware. Angle the transducer parallel to the waterline at speed for optimal performance—test at planing speeds and adjust brackets as needed.
Route the 30-ft cable away from electrical interference for clean signals.
Use marine sealant on mounting screws to prevent leaks.
Pair with high-definition Garmin units for split-screen views of traditional, ClearVü, and charts.
Regular maintenance like wiping salt residue and checking mounts keeps it performing like new season after season.
What’s Included for Quick Setup
GT21-TM 8-pin transom mount transducer
Complete mounting hardware kit
Detailed installation guide
Frequently Asked Questions
What makes ClearVü CHIRP different from traditional sonar?
ClearVü provides high-resolution, photo-like images directly below and beside your boat, revealing structure details that traditional sonar marks as arches. Together, they offer complete coverage for spotting fish and bottom contours.
