Raymarine ST300, Thru-hull Shorty™

Perfect for Boats with Tight Clearances: Unlock Precise Speed and Temp Data

Navigating the challenge of installing reliable speed sensors on vessels with minimal underfloor space? The Raymarine ST300 Thru-Hull Shorty stands out as a game-changer for sailors and powerboaters alike. Its ultra-compact design slips into spots where traditional transducers falter, ensuring you get accurate boat speed and water temperature readings without compromising hull integrity or performance. Ideal for fiberglass hulls, this sensor delivers real-time data to help optimize sail trim, monitor fuel efficiency, or fine-tune racing strategies—all from a barely-there profile that hugs the waterline.

Crafted with marine-grade plastic housings, it minimizes drag and turbulence, providing smoother data flow even at higher speeds. Whether you're cruising coastal waters or competing in regattas, this thru-hull solution proves that compact doesn't mean compromised.

Standout Design Features That Make Installation a Breeze

• Ultra-Low Profile Housing: Choose the P371 option that protrudes just 5mm (3/16 inch) beyond the hull exterior, slashing drag and ideal for shallow drafts or low-freeboard boats.
• Flush Countersunk Mount: The P398 housing sits perfectly level with the hull, banishing eddies for pinpoint speed accuracy—crucial for performance-oriented skippers.
• Minimal Headroom Needs: Requires only 153mm of vertical clearance, perfect for retrofits on older yachts or custom builds with cramped bilges.
• Smart Cable Routing: Right-angle exit keeps wiring tidy and protected against accidental steps or snags during maintenance.
• Fail-Safe Valve: Self-closing mechanism cuts water ingress instantly when the insert is pulled for cleaning, keeping your bilge dry and safe.

Technical Specs at a Glance

• Thru-hull mounting optimized for 0° to 22° deadrise angles—fits most planing hulls and sailboats.
• Generous 30-foot cable for flexible routing to your display helm.
• 200kHz frequency focused on speed and temperature sensing, no depth clutter.

Seamless Integration with Your Raymarine Ecosystem

Plug-and-play compatibility extends to a wide array of Raymarine instruments, making upgrades straightforward. Pair it effortlessly with i40, i50, ST40, ST60, ST60+, or ITC-5 displays for instant speed logs and temp alerts. It's also a solid match for legacy analog setups, breathing new life into older cockpits without full system overhauls. In competitive sailing, where every knot counts, this sensor feeds clean data to your instruments, helping you read true water speed versus GPS ground speed for smarter tactical decisions.

Boost Your Boating Performance and Efficiency

Beyond basic readings, the ST300 empowers proactive boating. Accurate speed data reveals hull fouling early, flags prop inefficiencies, or confirms optimal hull speed in varying conditions. Temperature insights warn of thermal layers affecting fish behavior or engine cooling risks. For racers, its low-drag profile shaves seconds off times by reducing wake interference. Trailered boats appreciate the easy-service design—no hauling required for routine checks. In essence, it transforms raw navigation into actionable intelligence, enhancing safety and enjoyment on every outing.

Pro Installation Tips for Peak Performance

Position forward of the propeller and straddle centerline for best flow. Angle the thru-hull 10-15° downward in the forward direction to match water entry. Use anti-fouling paint on the exterior paddlewheel sparingly to avoid imbalance. Fair the housing edges post-install for zero turbulence. Regular freshwater rinses post-saltwater use extend sensor life dramatically.

Simple Maintenance for Long-Term Reliability

Keep it spinning smoothly with quarterly inspections: Remove the insert via the self-closing valve, clean the paddlewheel with a soft brush and mild soap, then reinstall. Avoid high-pressure washes that could damage seals. In warm climates, check for marine growth monthly. This low-fuss routine ensures years of dependable service, rivaling bulkier competitors without the hassle.