The Walker 4020 Mk2 is a compact, MED Wheelmark type-approved Electromagnetic (EM) Speed Log system manufactured by John Lilley & Gillie Ltd. (Walker Marine Technology) in the United Kingdom. Designed for commercial merchant vessels, workboats, and coastal vessels with overall lengths up to 50 meters, the 4020 Mk2 combines the speed processing electronics and master speed/distance display into a single master unit (P282), minimizing installation footprint and sub-unit wiring complexity.

Operating via electromagnetic induction, the system measures Speed Through Water (STW) across both forward and astern ranges (-20 to +60 knots) with high linear accuracy unaffected by water depth, draft pressure, or salinity variations. The Walker 4020 Mk2 features a removable keypad calibrator, built-in speed simulator, multipoint calibration, and output interfaces (NMEA 0183 & pulse) for seamless integration with RADAR, ECDIS, VDR, and optional DIN 144 bridge repeater indicators.

Key Features:
• MED Wheelmark Type Approved: Certified speed log solution providing full SOLAS compliance for commercial vessels in a space-saving package.
• Integrated Master Unit: Combines speed processing electronics and dual red LED speed/distance displays into a single console- or bracket-mountable master unit.
• Wide Speed Range & Astern Sensing: Measures forward and astern Speed Through Water (STW) from -20 to +60 knots.
• Flexible Hull Transducer Options: Compatible with Walker fixed (P57) and retractable (P99 with GL-tested sea valve) electromagnetic sensors for steel, aluminum, GRP, or wood hulls.
• Integrated Calibration & Simulation: Equipped with a removable keypad calibrator for multipoint setup and a built-in speed simulator for system testing.
• Universal Bridge Outputs: Delivers standard NMEA 0183 (IEC 61162-1 / RS-422) serial data and dual 200 pulses per nautical mile (200 ppnm) contact closure outputs.