Autopilot for Catamarans: Twin Rudder Setup

Why a catamaran is a steering question, not a hull question

A catamaran has two hulls and, on most designs, two rudders. The helm connects both rudders through one steering system, so when you add an autopilot, the autopilot is not steering a rudder directly. Its drive unit interfaces with the vessel's steering system, as Raymarine states on its autopilot drive units page. That is the first fact to carry into any listing.

The practical result is that the steering type decides the autopilot, not the hull count. Hydraulic steering, mechanical cable steering, wheel steering and electronic helm systems each use a different family of drives. See drive types explained for the families. The pack title usually names the steering type it is built for. If the title says hydraulic, the drive in the pack is a hydraulic pump; if it says sail and wheel, the drive is a wheel drive.

Drive types you will see on listings

Raymarine's drive units page lists the families you will meet: cockpit tiller drives for tiller-steered sailboats, wheel drives for wheel-steered sailboats, hydraulic pumps for hydraulic steering, and rotary and linear drives for mechanical steering systems. Furuno's NavPilot line similarly names outboard and sterndrive packs around hydraulic steering.

On a catamaran, the two rudders do not change the drive family. What the twin rudder changes is the question you ask the seller: which steering system connects the two rudders, and does the drive in the box match that system. Torque, in general terms, is the turning force the drive applies to the steering; the maker's page answers that question by naming the drive family for each steering type. Hydraulic steering autopilots work with hydraulic helms, while mechanical steering uses rotary or linear drives.

Ask the dealer or an authorized installer if you cannot tell from the listing. That is the step the maker's own pages recommend, and this site gives no installation instructions.

Complete packs and core packs for a catamaran

A complete autopilot pack includes the drive, the control head in its named form, and the sensor. A core pack leaves the drive out, for a boat that already has a drive the buyer plans to keep. The difference is the first filter on this site.

For a catamaran, the same choice applies. If the existing hydraulic pump or linear drive is suited to the steering system, a core pack is the pick. If there is no drive aboard, a complete pack is the one that puts the system together. The maker's page for the pack names the steering type it serves, which is where the fit is decided. Read more about a core pack without the drive.

Sail and power catamarans

Listing titles signal the boat type. Raymarine's packs are named Power Pilot, Sail Pilot, Tiller Pilot and Wheel Pilot, each with a steering type in its description. Furuno's NavPilot 300 is built around outboard and sterndrive steering with hydraulic control.

A sail catamaran often has mechanical steering or hydraulic steering depending on size; a power catamaran frequently has hydraulic steering or an electronic helm. The pack that matches the title's steering type is the one to compare against your boat's steering. The difference between sailboat and powerboat autopilots comes down to the steering it is built for.

Heading sensor placement on a catamaran

The heading sensor in an Evolution autopilot is described by Raymarine as the autopilot central processor and 3D heading sensor at the heart of the system. Its location is a matter for the maker's manual and a qualified installer, not for a shopping guide.

On a catamaran, the bridge deck and the two hulls offer different magnetic surroundings. The principle, in general terms, is to place the sensor where the local magnetic field is steady and away from large metal masses and current-carrying wiring. The manual covers the exact rule; the installer applies it. Sensor requirements explain the general idea.

Ask your dealer about sensor placement when you get a quote. That is a normal part of the installation conversation, and it is one of the questions the maker's pages send you to a dealer for.

Questions to ask before you buy

Before you open a listing, write down three answers: the steering type (hydraulic, mechanical, wheel, electronic helm), whether a drive is already aboard, and whether you want a control head in the box. Those three answers map directly to the pack name.

Then read the maker's page for the pack: it names the steering type the pack serves. If the listing says the pack is for a powerboat with hydraulic steering, that is what it is for. If it says no drive or requires a pump, the drive question is yours to resolve. Multihull autopilot considerations cover the broader picture.

Finally, plan the installation as a question for the maker's manual and a qualified installer. This site gives no installation instructions, because the manual and the installer decide.

What to pick for your situation

Questions

Do I need a different autopilot because my boat is a catamaran?

Not because of the hull count. The autopilot is chosen for the steering system. The drive unit interfaces with the steering, so a hydraulic steering catamaran uses the same family of hydraulic pump drives as a monohull with hydraulic steering.

Does the twin rudder change the drive I need?

It changes the question you ask, not the drive family. The two rudders are connected through one steering system. The maker's page names which drive suits which steering type, and the dealer or an authorized installer can confirm the drive for your rudder arrangement.

Where should the heading sensor go on a catamaran?

The maker's manual and a qualified installer decide the location. In general, the sensor should sit where the magnetic field is steady and away from large metal objects and current-carrying wiring. The bridge deck and the hull ends give different surroundings, which is exactly why the manual matters.

What does 'w/o GHC' mean in a listing title?

It means the pack is sold without the control head in the box. The control head is the interface you use to operate the autopilot. If you already have a compatible control head, that is fine; if not, the control head is a separate purchase.

Is a core pack enough for a catamaran?

A core pack is enough when the drive is already aboard and suited to the steering system. The maker's page for the pack decides the fit. If there is no drive, a complete pack is the one to compare.