Raymarine ST4000MK2 / ST4000+ Wheel Drive E12093 (Drive Only)

The Raymarine ST4000MK2 / ST4000+ Wheel Drive (part E12093) is the wheel-mounted autopilot drive unit for the Raymarine ST4000 MK2 and ST4000+ sailboat autopilot systems. Clamps directly to the boat's steering wheel via the included clamping hardware - the autopilot drives the wheel directly when engaged, just as a helmsman would. It's the right autopilot drive solution for sailboats with cable-and-quadrant steering systems where running mechanical or hydraulic steering linkage modifications for a below-decks autopilot drive isn't practical or worth the install cost.

Important: drive only, not a complete autopilot. This package contains the wheel drive UNIT ONLY. To make a complete functional autopilot system, you also need: the ST4000 MK2 or ST4000+ control head (the helm display and computer), the autopilot's heading sensor (typically a fluxgate compass mounted in a stable interior location), the SeaTalk network cabling for connecting the components together, and the necessary 12V power wiring with appropriate fuses. It's the replacement / spare drive component for boats that already have an ST4000 MK2 / ST4000+ control head installed and need a new drive unit because the original failed, or for owners building up an ST4000-class autopilot from individual components rather than buying a complete bundled kit.

How wheel-driven autopilot works. Wheel-drive autopilots take a different approach from the more familiar below-decks linear-actuator autopilots. Instead of installing a hydraulic or mechanical actuator down below the cockpit on the steering linkage, the wheel drive sits in the cockpit and drives the steering wheel directly. The autopilot's drive belt wraps around the wheel hub and the drive motor turns the belt to rotate the wheel exactly as a helmsman would. Net advantage: install simplicity (no below-decks linkage work, no hydraulic plumbing). Net trade-off: the wheel drive sits visible in the cockpit, and the wheel can't be locked off when the autopilot's engaged (the drive turns the wheel, so the helm has to be free to rotate).

Adjustable clutch lever. The drive's clutch lever lets you instantly engage or disengage the autopilot's connection to the wheel. Engaged: the autopilot turns the wheel via the drive belt. Disengaged: the wheel spins freely for hand-steering, and the autopilot drive is free of the wheel. The instant switching matters for the constant-attention conditions you'll see on a sailboat (close-quarters maneuvering, weather changes, sail trim adjustments) where you want to drop autopilot and grab the wheel without waiting for any disengagement procedure. Pull the lever, take the wheel.

Fits wheels with 3, 4, 5, 6, 7, or 8 spokes. The drive's wheel-clamping hardware is engineered to fit standard sailboat steering wheels in any of the common spoke counts (3, 4, 5, 6, 7, or 8). The drive belt wraps around the wheel hub between the spokes. Standard wheel diameters are accommodated. For unusual or non-standard wheels you'll find on some boats (e.g., teak destroyer wheels with 10 or 12 spokes, or aluminum spec-class racing wheels with unusual hub geometry), check the install instructions for compatibility before assuming fit.

1 to 3.5 turns lock-to-lock. The drive accommodates steering systems with 1 to 3.5 turns lock-to-lock (the number of full wheel rotations from full-port-rudder to full-starboard-rudder). Most standard production sailboats fall in the 2 to 3 turns range. Below 1 turn (very direct steering) the autopilot may be over-sensitive. Above 3.5 turns (very heavily geared steering, typical only of large traditional yachts) the autopilot's response time may be too slow for effective course-holding. Check your boat's steering specs against the 1 to 3.5 range before assuming compatibility.

For sailboats up to 7,500 kg laden displacement. The recommended boat-size limit is 7,500 kilograms (about 16,500 pounds) of fully-loaded sailboat displacement. That covers most cruising sailboats from about 28 to 38 feet at typical loaded weight. For larger sailboats above 7,500 kg laden displacement, the wheel drive's torque output isn't sufficient to overcome the steering loads in heavy weather - those boats need a more powerful below-decks linear actuator instead (the Raymarine Type 1 / Type 2 / Type 3 drive line in combination with an EV-100 / EV-200 / EV-400 autopilot).

SeaTalk-compatible operation. The drive connects to the ST4000 MK2 / ST4000+ autopilot control head via the standard SeaTalk autopilot cabling. SeaTalk is Raymarine's proprietary marine instrument network protocol (later evolved into SeaTalkNG which is fully NMEA 2000 compatible). The original SeaTalk used in the ST4000 MK2 generation is the legacy 3-wire connection. For boats that have evolved to SeaTalkNG / NMEA 2000, an adapter cable bridges the legacy SeaTalk autopilot drive to the modern network.

Cockpit-mounted vs. below-decks. Wheel-drive autopilots are visible in the cockpit at all times when installed. For owners who prefer a clean uncluttered cockpit, below-decks linear-actuator autopilots are the cleaner option but require significantly more install work (cutting and modifying the steering linkage, plumbing hydraulic lines for hydraulic drives, etc.). The wheel drive is the right choice for owners who prioritize install simplicity and cost over visible aesthetics.

Construction. Marine-grade aluminum and stainless steel construction with a fully-enclosed gear case to keep saltwater spray out of the drive mechanism. Painted gray housing with silver-tone wheel-clamping hardware. Built to handle the marine environment over years of typical sailing service.

Compatibility note. The E12093 Wheel Drive specifically fits the ST4000 MK2 and ST4000+ autopilot systems. For older first-generation ST4000 (without the MK2 / + designation), the older E10039 wheel drive is the compatible variant. For newer Raymarine Evolution-series autopilots (EV-100 Wheel, EV-200 Wheel), those use a different wheel drive variant - check the specific autopilot model compatibility before assuming fit.

What's in the box. The wheel drive unit (with motor, gear case, drive belt, clutch lever, and wheel-clamping hardware), install instructions, mounting hardware. Required separately: ST4000 MK2 / ST4000+ control head, heading sensor (fluxgate compass), SeaTalk cabling, 12V power wiring, all standard install accessories.

2-year limited Raymarine warranty. Same-day shipping before 3 PM ET on in-stock units.