Speed
Marine Speed Instruments & Log Sensors
Measure boat speed through water and distance traveled with professional marine speed instruments. Our collection features speed sensors and displays from Raymarine, B&G, Simrad, and Garmin:
- Paddlewheel Speed Sensors - Traditional through-hull speed measurement
- Sonic Speed Sensors - No moving parts, maintenance-free
- Speed/Temp Sensors - Combined speed and water temperature
- Speed Displays - Dedicated speed and log displays
Essential for navigation, performance monitoring, and accurate dead reckoning. All sensors integrate via NMEA 2000 or NMEA 0183.
Complete Instrumentation: Part of our Instruments collection. Combine with wind, depth, and multifunction displays. Connect via NMEA 2000 to autopilots and chartplotters for complete vessel data.
Paddlewheel or sonic: which speed sensor
Paddlewheel sensors are the traditional choice: a small impeller sits in the water flow and its rotation is converted to a speed reading. They are inexpensive and easy to service, but the impeller can foul with weed or marine growth, which shows up as an erratic or low reading long before anyone notices the sensor needs cleaning. Sonic sensors measure speed by timing an ultrasonic pulse through the water instead, so there is nothing to foul or wear, though they cost more and can be affected by aerated water under the hull in a seaway.
Either type needs calibrating against a known reference, typically GPS speed over ground on a flat calm day, since boat speed through water and speed over ground diverge whenever there is tide or current running; without calibration the instrument reading can be out by a knot or more. A retractable through-hull fitting is worth considering for paddlewheel sensors, since it lets the impeller be pulled and cleaned without hauling the boat.
