Overview

The Simrad 000-15621-001 is a NAC-D autopilot computer for steer-by-wire electronic vessel control systems that use a digital steering interface. It connects on NMEA 2000 using two Micro-C ports and draws power from the network (9 to 16 V via CAN, 2 LEN, 40 mA typical), so it fits cleanly into an existing NMEA 2000 backbone.

Because it works on a digital steering bus, there is no need to add a hydraulic pump, install a rudder feedback sensor, or run a dockside rudder calibration as part of the autopilot install. The unit is small (86.5 x 20.0 x 11.5 mm) and is intended for a protected below-decks mounting location; it carries an IP44 rating, so it should be kept out of direct spray and heavy washdowns.

Key features

• Steer-by-wire autopilot computer for electronic vessel control systems with digital steering interfaces.
• Approved interface support for SeaStar Optimus, Yanmar VC10/JC10, Volvo IPS/EVC, and Yamaha Helm Master and single-engine control systems.
• NMEA 2000 connectivity with two Micro-C ports (2 LEN).
• Powered from the NMEA 2000 network (9 to 16 V via CAN) with low current draw (40 mA typical).
• Two speed profiles with Continuum steering logic, with SteadySteer functionality for smooth transitions between hands-on steering and autopilot steering.
• Supports steering to headings and routes, plus turn patterns including C-turn, U-turn, zigzag, square turn, S-turn, and depth contour tracking when supported by the control interface.
• Operating temperature range 0 C to 55 C, and a 0.5 m compass safe distance for placement planning.

Compatibility and fit

This autopilot computer is for boats that already have a compatible steer-by-wire control system with a supported digital interface. It is not a drop-in replacement for a hydraulic pump based autopilot, and it is not meant for cable steer, mechanical steering, or traditional hydraulic autopilot plumbing.

Control can be handled through compatible Simrad autopilot controllers such as the AP44 or AP48, and it can also be integrated with compatible Simrad multifunction displays. A NMEA 2000 heading sensor is required on the network for autopilot operation, and all devices should be set up so the system is pulling heading, speed, and navigation data from the intended sources.

Installation and setup

Plan for a dry, protected mounting location below decks since the housing is IP44. Keep it away from direct bilge water, deck wash spray paths, and high-heat zones, and maintain at least 0.5 m separation from a magnetic compass.

On the network side, the NAC-D expects a properly built NMEA 2000 backbone with correct termination and adequate power. Once everything is online, the autopilot still needs commissioning and setup through the chosen control interface so steering behavior, vessel type, and on-water tuning are matched to the boat.

Use on board

This is a strong fit for boats with modern electronic vessel control that want autopilot functions without adding pumps and feedback hardware. It is commonly used on offshore runs and long coastal legs where course keeping and route following reduce helm workload, while still allowing quick manual steering input when conditions change.

Maintenance and care

Periodically inspect the Micro-C connections for corrosion or looseness, keep the unit clean and dry, and confirm the NMEA 2000 backbone remains properly powered and terminated. If the network is modified or devices are replaced, re-check source selection and autopilot setup so the system is using the correct heading and navigation data.

What’s included

• NAC-D autopilot computer
• N2K-T-RD Network T-Connector