How to Select the Right Autopilot Hydraulic Drive

05 October 2022

How to Select the Right Autopilot Hydraulic Drive

Understand pump sizes and steering cylinder capacities

Autopilot Drives for Hydraulic Steering Systems

Raymarine Evolution pilots connect to hydraulic steering systems using a rugged hydraulic pump matched to the capacity of the hydraulic steering system. To match an autopilot pump to a steering system, you will need to determine the volume of your steering system's hydraulic cylinder ram or rams(s) mounted to the rudder on inboard engine boats, or the cylinder mounted to the drive unit on an outboard engine. The hydraulic cylinder ram volume is measured in cubic inches or cubic centimeters. Your steering system documentation should have your steering cylinder volume size. Use the table below to determine which Evolution autopilot pump is a match for your steering ram's capacity.   

Type .05 Hydraulic Autopilot pump

Hydraulic Drive Steering Ram Capacity Guide

Evolution Hydraulic Drive TypeType 0.5 Type 1Type 2Type 3 Constant Running
Supported steering ram capacity 


(3.1 in3–6.7 in3)

80cc – 230cc

(4.9 in3–14 in3)

230cc – 350cc

(14 in3–21 in3)

350cc – 500cc

(21 in3–30.5 in3)

500cc - 1200cc

(30.5 in3 - 73 in3)

Compatible Evolution ACUACU-100

ACU-150 (12V)

ACU-200 (24V)


Tech Tips

  • If you cannot find the ram size in your steering system documentation, you can look on the cylinder ram itself for the brand and model number. Once you have the model number use our hydraulic cylinder ram cross-reference guide to determine which hydraulic autopilot pump is compatible with your vessel's hydraulic steering system.
  • An authorized Raymarine dealer is best suited to installing a hydraulic autopilot system.
  • In systems with dual steering rams in parallel, cylinder capacity is the total of both rams. Rams in series only require a single capacity valve. 
  • Hydraulic steering systems with steering rams over 500cc require our larger constant running pump used in conjunction with the relevant ACU - contact Raymarine for details.
  • Type 0.5 pump is suitable for Volvo D4/D6 Sterndrive applications.