M81137 Type 2 Rotary Drive Unit (24V)

The Raymarine Type 2 Rotary Drive (24V) is the flagship rotary drive unit, designed to deliver automatic steering for large vessels that utilize a 24-Volt electrical system. With this model, Raymarine addresses the needs of yachts and ships running on 24V that require an autopilot drive with high power without sacrificing performance. The M81137 carries all the attributes of the 12V version – including the capability to steer vessels up to 20 tons – but leverages the advantages of a 24V supply: lower current for the same output and potentially longer motor life due to reduced stress.

Installation of this drive is identical to other rotary models – it is inserted into the steering chain mechanism and takes over turning the helm wheel when the autopilot is active. Given the scale of the vessels it’s meant for, the M81137 is built with an extremely robust mechanical architecture. Its 24V motor is optimized for continuous operation; at 24V, it typically draws half the current for an equivalent power output compared to 12V, meaning less heat generation and higher efficiency. This is especially important for long passages where an autopilot may run continuously for hours or days on end.

The M81137 is controlled by the ACU-400, which ensures precise handling and integration with the Evolution autopilot system. Coupled with Raymarine’s gyro-stabilized sensor and course computer, the system can proactively react to course changes, instantly sending commands to the powerful 24V rotary drive. Even in heavy conditions – such as large ocean swells or maneuvering in strong crosswinds – the device responds reliably, swinging the rudder with the needed force to maintain the heading.

Practical use cases: The M81137 is an ideal solution for large motor yachts, expedition vessels, or commercial workboats that commonly feature 24V onboard power. For example, a 55-foot motor yacht with dual helms or an expedition sailboat can deploy this drive to maintain precise steering over long journeys. It allows the crew to set the course and rely on the autopilot for stability while they manage navigation or rest.

Advantages:

• Energy efficiency: In 24V systems, cables and components generally run cooler for the same power, which benefits high-current devices like autopilot drives. The M81137 capitalizes on this – the lower current draw reduces losses and allows the use of lighter gauge wiring without overheating. This can simplify installation, since the existing 24V infrastructure on board is already optimized for efficient power transmission.
• High reliability in professional use: For professional applications (e.g., patrol boats, commercial fishing vessels, passenger ferries), the 24V rotary drive offers the combination of strength and endurance needed. It’s designed to operate continuously in autopilot mode – as is often the case for these vessels – and to withstand constant maneuvering without motor burnout.
• Compatibility with 24V systems: Many larger boats have other 24V systems – winches, bow thrusters, heavy-duty lighting, etc. The M81137 fits naturally into such an environment without need for converters or separate 12V supplies, which simplifies the electrical setup and reduces potential failure points.
• Seamless switch-over between manual and auto: Like all Raymarine drives, safety is paramount – when the autopilot is disengaged or power is lost, the clutch immediately frees the helm so it can be turned by hand. For a captain of a big vessel, this means you can take control instantly if needed, without fighting any mechanical resistance. This immediate access to manual steering is crucial when docking or in emergency situations.
• Maintenance and monitoring: 24V systems on larger boats often come with more sophisticated monitoring. In this context, the ACU-400 driving the M81137 can be integrated to report status and faults to a central system. This is useful for crew to know if, for example, the drive is encountering unusual resistance or overload. Additionally, components like motor brushes, if they wear over time, can be serviced by authorized technicians to extend the unit’s lifespan.

In conclusion, the M81137 Type 2/24V Rotary Drive gives large boat owners confidence in their autopilot, providing a powerful, efficient, and well-integrated means of automatic steering. It’s a cornerstone of any long-range navigation suite that proves its worth by performing flawlessly when you need it most – out on the open ocean or during long overnight watches, where the machine takes the wheel and you trust its precision and durability to guide you.