M81135 Type 1 Rotary Drive Unit (12V)

The Raymarine Type 1 Rotary Drive (12V) is a trusted solution for automating the steering of boats with chain-and-sprocket helms. This drive unit installs behind the helm station, integrating into the steering chain so that when the autopilot is engaged, it turns the helm via the chain and sprocket just as if an invisible hand were at the wheel. With the capability to handle vessels up to 11 tons, the M81135 is ideal for mid-sized sailboats and motor yachts that need a dependable autopilot drive without the bulk of hydraulic systems. Its compact and robust construction delivers approximately 20 Nm of output torque – sufficient to maneuver the rudder under typical conditions for boats in its class. Powered by the boat’s 12V supply, the drive operates efficiently (drawing on the order of 24–48 W on average) and features a built-in clutch and reduction gear that protect the unit from overload. When active, the rotary drive’s motor quietly turns the helm, meaning the autopilot can work without adding noticeable noise to your cockpit environment.

Upon installation, the M81135 interfaces with the Raymarine ACU-200 actuator control unit, which manages its power and communications with the autopilot’s course computer. This allows the Evolution autopilot system to intelligently steer the vessel, continually making fine rudder adjustments through the rotary drive to keep the set heading. Depending on your steering system, you may need an appropriate sprocket or chain adapter to link the drive, but once connected, the unit becomes a seamless part of your steering mechanics. Crew and guests will appreciate the smooth operation – as the autopilot makes turns, the rotary drive moves the wheel fluidly without sudden jerks, maintaining comfort and control.

Applications and advantages:

• Perfect for cruising sailboats and powerboats: The M81135 is optimized for boats in the ~30–40 ft range where a mechanical steering system can be enhanced with autopilot functionality. Whether you’re a shorthanded sailor on a coastal cruiser or a captain of a sport-fishing boat, this drive relieves you from constant manual steering. It shines during long motoring passages or when trolling for fish, holding the course so you can focus on navigation, sail trim, or scanning for birds and bait.
• Precise course-keeping: In tandem with the EV-1 sensor and Evolution AI algorithms, the rotary drive helps the autopilot adapt to changing sea conditions with ease. For instance, as the boat pitches or rolls in waves, the autopilot will automatically adjust the rudder via the rotary drive to counteract deviations, resulting in a straighter track and even potential fuel savings due to reduced zig-zagging. The drive’s responsiveness (about 10 seconds hard-over to hard-over) means it can quickly correct the heading before minor deviations become major, which is particularly valuable in gusty wind or following seas.
• Reliability & safety built-in: The drive’s mechanical design incorporates a rugged gearbox and a clutch that slip or disengage to prevent damage if the rudder is forced or hits a stop. If you ever need to abruptly take the helm (for example, to avoid debris or traffic), you can simply switch the autopilot to standby; the clutch immediately frees the helm, handing full control back to you instantly. This fail-safe feature ensures that manual steering is always just a button-press away, giving skippers confidence in the autopilot system’s integration with the steering.
• Compact installation: The M81135’s small footprint allows it to be installed in tight spaces behind the dash or near the steering pedestal. It does not clutter the helm area and can be retrofitted to many existing mechanical steering setups. Raymarine provides detailed installation instructions, and their network of dealers can assist to ensure the drive is fitted correctly. Once installed, it’s neatly out of sight, preserving the helm station’s appearance and space.
• Low maintenance requirement: This rotary drive is engineered for long service life with minimal upkeep. It comes pre-lubricated and sealed; there are no regular lubrication points that the user needs to service. Periodic inspection of the chain tension and electrical connections is usually sufficient. This means you can depend on the drive to function trip after trip, season after season, with very little intervention – an important consideration for cruisers and professionals alike.

In summary, the M81135 Type 1 Rotary Drive Unit adds reliable automated steering to smaller and mid-size boats without complexity. By taking over the helm with quiet efficiency, it frees you to enjoy the journey or tend to other tasks, all while maintaining an accurate course. From coastal cruising to sport-fishing, this rotary drive enhances your autopilot system, making your time on the water safer and more relaxing by handling the helm duties with skill and endurance.