Navico Pump-2 MK2 Reversible Hydraulic Autopilot Pump 12V

The Navico Pump-2 MK2 is the mid-class hydraulic autopilot pump in the Navico autopilot product family - sized for mid-size boat hydraulic steering systems with cylinder displacement in the 80-250 cubic-centimeter range. The MK2 designation indicates the second-generation refresh of the original Pump-2: same form factor and performance specifications as the original, with updated internal seals and bearings for longer service life and improved cold-weather operation. For boats running Navico-family autopilot controllers and needing the right pump for the steering system, the Pump-2 MK2 is the appropriate match.

What this pump actually does. In a hydraulic-steering autopilot installation, the autopilot consists of three functional pieces. The autopilot computer (the NAC-2 or AC-12 controller, sold separately) is the brain that takes navigation commands from the chartplotter or the dedicated autopilot keypad and decides what rudder corrections to make. The pump (this Pump-2 MK2) is the muscle that takes the controller's commands and converts them into hydraulic flow that drives the steering cylinder. The cylinder is the actuator that physically pushes the rudder. The Pump-2 MK2 is the middle piece - it doesn't decide what to steer, it just drives the cylinder when the controller says so.

Reversible gear pump design. The Pump-2 MK2 uses an internal hydraulic gear pump that can run in either rotational direction - controlled electrically by reversing the polarity on the pump's motor leads. When the autopilot controller wants to steer right, it applies positive voltage to one motor lead and negative to the other - you'll see the pump run in one direction, drive fluid into one side of the steering cylinder, and the rudder rotate right. When the controller wants to steer left, it reverses the polarity. the pump runs in the opposite direction, drives fluid into the opposite side of the cylinder, and the rudder rotates left. The reversible design eliminates the need for separate forward / reverse pumps or for solenoid valves to redirect flow direction.

80-250 cc cylinder displacement compatibility. The Pump-2 MK2 is sized for steering cylinders with internal displacement (the volume of fluid required to push the piston from full-port to full-starboard) in the 80 to 250 cubic-centimeter range - which translates to roughly 4.9 to 15.2 cubic inches in U.S. measure. This covers the typical mid-size recreational boat range: most outboard hydraulic steering cylinders, most inboard / I/O hydraulic steering systems on boats from roughly 25 feet to 40 feet length-overall, and most stern-drive hydraulic steering systems. For smaller boats with smaller cylinders (under 80 cc), the smaller Pump-1 MK2 is the right match. For larger boats with bigger cylinders (over 250 cc), the larger Pump-3 or Pump-4 are the appropriate options. Verify your cylinder's displacement before ordering - if you don't, the pump may be over- or under-sized for your steering system.

0.8 liters per minute flow rate. The Pump-2 MK2 delivers 0.8 liters per minute (roughly 49 cubic inches per minute) of hydraulic flow at typical autopilot operating conditions. This flow rate is engineered to match the response time the autopilot needs - fast enough to make timely course corrections without lagging the boat's actual steering response, slow enough to deliver smooth steering without jerky over-correction. The flow rate is the result of careful tuning between pump displacement, motor speed, and the typical steering geometry the autopilot drives.

O-Ring Boss (ORB) port connections. The Pump-2 MK2 has ORB ports (the modern hydraulic port standard that uses an O-ring face seal, meaningfully more leak-resistant than older NPT thread-sealed ports). The included three ORB-5 to 9/16 UNF adapter fittings convert the ORB ports to the more common 9/16-18 UNF (also known as JIC-6) port standard used in most marine hydraulic plumbing. Three fittings cover the typical install: one for each of the two cylinder ports plus one for the bypass / vent line. For installs that need different adapter types, hydraulic supply vendors carry ORB-to-anything adapters in standard configurations.

12V DC operation. The Pump-2 MK2 runs on standard 12V DC marine power. Current draw is moderate - typical operating current is 3-5 amps under load, peak current at full-pressure operation can briefly hit 8-10 amps. Wire to the boat's autopilot circuit through the typical 15-amp circuit fuse on a dedicated autopilot circuit. The autopilot controller (NAC-2 or AC-12) typically provides the pump's switched power output, so the pump connects directly to the controller rather than to the boat's main accessory bus.

SteadySteer compatibility. SteadySteer is the Navico autopilot intelligence layer - the software / firmware that runs on the autopilot computer and provides the steady-course feel that gives the SteadySteer name. SteadySteer is engineered for boats with hydraulic outboards, sterndrives, or inboards using a hydraulic ram - and the Pump-2 MK2 is the supported pump variant for this use case. The combination delivers the modern Navico autopilot performance: precise course-keeping with minimal yaw, smooth course corrections without over-correction, and the responsive feel that SteadySteer is known for among Navico autopilot users.

Compatible autopilot controllers. The Pump-2 MK2 works with the Navico-family autopilot computer line: NAC-2 (the SteadySteer-class autopilot computer for the Navico-family system) and AC-12 (the autopilot computer for the broader Navico autopilot product line). Both controllers are sold separately - the Pump-2 MK2 is the pump component only, not a complete autopilot system. For a complete install, you need the autopilot controller, the Pump-2 MK2 (this part), the steering cylinder (typically already installed as part of the hydraulic steering system), the rudder feedback unit (for some applications), and the autopilot keypad / display interface.

Corrosion-resistant marine construction. The pump's housing and internal hardware are corrosion-resistant materials suitable for the marine environment. The motor windings are sealed against moisture intrusion. The hydraulic seals are engineered for long-term marine service life - typical service interval is 5-10 years before any seal refresh is needed. For boats in saltwater service, rinse the pump's exterior with fresh water occasionally and apply a corrosion inhibitor to the connector terminations.

Install. Mount the pump on a flat surface in the engine room or steering bay, oriented per the install guide for proper hydraulic flow. Plumb the pump's two cylinder ports to the steering cylinder's two ports using marine-grade hydraulic hose with the appropriate ORB / JIC adapters. Connect the pump's motor leads to the autopilot controller's switched output. Bleed the entire hydraulic system per the install instructions (a critical step - air in the lines causes spongy steering and erratic autopilot behavior). Total install time is typically 4-8 hours for a competent marine technician with hydraulic and autopilot experience.

What's in the box. The Pump-2 MK2 pump assembly with attached motor leads, three ORB-5 to 9/16 UNF adapter fittings, basic install documentation. Required separately: the autopilot controller (NAC-2 or AC-12), hydraulic hose / fittings to your specific install dimensions, marine hydraulic fluid (typically Lubex or similar marine-grade ATF / hydraulic fluid spec), the bleed kit, and any additional adapter fittings for non-standard plumbing.

Standard Navico warranty applies. Service runs through the Navico authorized service network.