Upgrade your marine sonar experience with the Raymarine B175LM 20-degree thru-hull CHIRP transducers, designed as a reliable pair for serious anglers and navigators. These transducers deliver exceptional target separation and depth penetration, transforming how you detect fish, structure, and bottom contours even in challenging conditions. Mounted directly through the hull, they provide clean, real-time data without the drag or interference of transom mounts, making them ideal for planing hulls and larger vessels chasing trophy catches in deep offshore waters.

What sets this pair apart is their ability to operate independently or in tandem, offering redundancy and broader coverage. Whether you're marking bait schools at 3,000 feet or navigating wrecks with pinpoint accuracy, the B175LM's wide CHIRP bandwidth ensures crisp, high-resolution images that reveal what basic sonar can't.

Powerful Dual-Channel CHIRP Performance

The B175LM combines low and medium-frequency CHIRP channels in a single housing, sweeping across broad spectrums for unmatched versatility. Low frequencies punch through thermoclines and sediment for maximum depth, while medium frequencies excel at resolving fine details like individual fish or tight weed lines. With a 20-degree beam angle, each transducer focuses energy efficiently, minimizing side clutter and maximizing central target returns—perfect for high-speed trolling or precise spot-locking.

• Low CHIRP: 42-65 kHz for deep-water prowess up to thousands of feet.
• Medium CHIRP: 84-108 kHz for sharp mid-range imaging.
• 20° Beam: Balanced coverage without sacrificing resolution, suited for hulls 30 feet and up.
• Pair Configuration: Install one forward and one aft for continuous coverage or backup reliability.

Built for Harsh Marine Environments

Crafted from marine-grade bronze with a hydrodynamic shape, these transducers withstand constant water pressure, corrosion, and impacts from debris. The urethane front face optimizes acoustic transmission while protecting internals from biofouling. Over time, this durability means fewer replacements and consistent performance, even after seasons of saltwater exposure.

Pro tip: For fiberglass hulls, fairing blocks ensure dead-flat mounting to avoid air pockets that distort readings. In aluminum or steel hulls, proper deadrise matching prevents signal loss.

Seamless Integration with Modern Fishfinders

These thru-hulls connect effortlessly to Raymarine's Axiom, Axiom Pro, and Element series via standard 8-pin or FAKRA connectors, unlocking DownVision, SideVision, and RealVision 3D capabilities. Pair them for dual-screen setups or multi-engine boats, and enjoy software-updatable firmware for evolving features like ForwardScan compatibility.

Users report game-changing clarity when combined with Lighthouse chartplotters, spotting suspended game fish that transom units miss at planing speeds above 25 knots.

Installation Insights for Peak Performance

Thru-hull installs demand precision, but the B175LM simplifies it with a compact 1.8-inch diameter footprint. Core out your hull at the lowest deadrise point forward of any strakes, typically 1/4 hull length from the bow. Use marine sealant like 4200 for watertight seals, and route cables away from engines to dodge EMI noise.

For the pair: Position one at 18-24 degrees port/starboard offset for stereo-like coverage. Test in calm water post-install to calibrate gain and verify no air entrainment—adjust fairing if bubbles appear on screen.

"Switched from in-hull mounts and immediately saw doubled depth range. Fish arches pop like never before." – Experienced offshore captain.

Why Boaters Trust the B175LM Pair Over Singles or Alternatives

A single B175LM shines, but the pair delivers failover protection and zoned scanning—forward transducer for search, aft for tracking. Compared to wider-beam options, the 20-degree focus cuts noise in cluttered bays, while narrower ones lose coverage. It's the sweet spot for bluewater pros who demand zero downtime and pro-grade intel.

Enhance returns with routine hull cleaning and winter storage in freshwater; this extends transducer life beyond five years easily.

Frequently Asked Questions