Upgrade your boat's navigation with the precision and reliability of a thru-hull speed and temperature sensor designed for serious mariners. This retractable model delivers unmatched responsiveness from idle speeds up to high-velocity runs, ensuring you always know your boat's performance without guesswork. Its sleek, low-drag design integrates seamlessly into fiberglass or metal hulls, making it a favorite among sailors, racers, and cruisers who demand accuracy in dynamic conditions.

Superior Speed Detection That Starts Fast and Stays True

What sets this sensor apart is its advanced Gen2 paddlewheel technology. Unlike older models that lag at low speeds or falter at high ones, it kicks in reliably at just 0.3 knots and holds steady through 45 knots. Imagine docking with confidence or pushing limits on open water—every reading is smooth, linear, and trustworthy. Pair that with rapid water temperature updates, and you've got real-time data for optimizing fuel efficiency, engine performance, or even fishing spots where temp changes signal bites.

Streamlined Design for Minimal Drag and Maximum Protection

Crafted to hug the hull with only a 5mm protrusion, this low-profile thru-hull unit cuts through water like it's not even there, preserving your boat's speed potential. The retractable valve is a game-changer: pull the core for cleaning or winter storage, and it seals tight to keep bilge water at bay. Choose plastic housing for versatile fiberglass setups or bronze for metal hulls—either way, durability meets everyday boating demands.

Effortless Integration with Your Raymarine Setup

Analog output makes it plug-and-play with popular displays like i40, i50, or iTC-5 instruments, plus it's backward-compatible with legacy Raymarine systems. For those upgrading older Airmar P120 or B120 housings, the ST900 core drops right in—no major refits needed. This modularity saves time and hassle, letting you focus on the water instead of wiring.

Pro Tips for Installation and Peak Performance

Mount it forward of props and keels for clean water flow, ideally at the hull's flattest spot below the waterline. Drill a precise 51mm (2-inch) hole, bed it in sealant, and secure with the included nut. During install, flush the paddlewheel regularly to fend off marine growth—freshwater rinses after saltwater trips keep it spinning like new. In cold climates, retract it fully to avoid freeze damage. With a generous 13.7m cable, routing to your helm is straightforward, even on larger vessels.

• Best for: Sailboats, power yachts, fishing rigs—any hull craving precise speed logs.
• Temp sensing shines: Tracks shifts from 14°F to 104°F, vital for engine cooling or thermocline hunting.
• Maintenance hack: Valve lets you service without hauling out—perfect for liveaboards.

Real-World Reliability from Seasoned Boaters

Mariners rave about its low-speed startup, which outpaces competitors during tight maneuvers or light winds. High-speed linearity means GPS cross-checks match perfectly, building trust in your data. Whether racing around buoys or cruising coastal waters, this sensor proves why Raymarine leads in marine tech—robust, responsive, and built to last through salt, sun, and storms.