Compared across 4 stores. Prices are checked against each store and labelled with when. Store links may earn us a commission. Price via Klarna.
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The GT21-TM is a transom-mount all-in-one transducer that pairs traditional 50/200 kHz CHIRP sonar with Garmin's ClearVü down-scanning sonar. It covers deep water with traditional sonar and shows structure and bottom detail with ClearVü, so one unit replaces two hull fittings. It suits boaters with a compatible Garmin chartplotter who fish both open water and structure. Against single-frequency transducers it adds down-scanning detail; against Garmin's higher-end GT models it gives up side-scanning and some high-frequency CHIRP performance.
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Lowest price we've seen: $138.12 on Nov 9 at TWIST. Tracked across 4 stores since Nov 9.
Owners of compatible Garmin units generally find the GT21-TM a solid step up from a basic transducer, with clear down-scanning images in shallow to mid depths. Complaints center on high-speed performance and on fitting it to the right unit.
The Garmin GT21-TM is a transom-mount transducer that supports CHIRP and DownVu sonar. It connects with an 8-pin connector.
For traditional sonar, the maximum depth is 1500 ft and the operating frequency is 50/200 kHz. For ClearV, the maximum depth is 1000 ft and the operating frequency is 260/455 kHz. The transducer is designed for transom angles from 0 to 70 degrees.
