Autopilot Power Draw: How Much Is Enough?

Voltage and draw: what a listing states

Autopilot listings on this site name the parts in the box: the control head, the course computer or actuator control unit, the heading sensor and the drive. They rarely name how many amps a component draws. That is a detail the maker's page or the maker's manual carries, and this site compares only the stated details you see in a listing.

A listing does state the voltage a pack expects. For example, the Furuno NavPilot 300 page states 12-24 VDC, and the Raymarine page for the Type 0.5 hydraulic pump says it is for boats with 12-volt power systems. Reading those words tells you whether the pack matches the electrical system your boat already has.

Which parts of an autopilot use power

A complete autopilot system has the same job no matter the brand: read a heading, decide the correction, and move the steering. The parts that use power are the control head you press, the course computer or actuator control unit that holds the software, the heading sensor that reports the boat's direction, and the drive that does the work on the steering.

The control head is the panel you read and touch. The course computer is the brain. The heading sensor keeps pointing at the boat's direction. The rudder reference reports how far the rudder has turned. Of these, the drive is the part that deserves attention in a power budget, because moving the steering is the job that asks for real work. You can compare drives by name in the drive types article and see which packs include them in the complete pack guide.

• Control head: the panel with buttons, a knob or a touch screen.
• Course computer or actuator control unit: the processor that decides the correction.
• Heading sensor: the compass that reports the boat's direction.
• Drive: the linear, rotary or hydraulic unit that moves the steering.
• Rudder reference: the feedback that reports rudder position where a pack includes it.

The drive is where the work happens

The drive comes in a few named forms. A linear drive pushes a rod along a track. A rotary drive turns a shaft. A hydraulic pump moves fluid to the boat's hydraulic steering. A tiller pilot is a self-contained unit with the electronics and the drive in one body, mounted at the cockpit for tiller-steered sailboats.

Which drive a boat needs is decided by the steering type and the boat's size and weight, as the maker's pages say. This article cannot tell you that a drive is right for your boat; the maker's stated details and a qualified installer's answer are the places to settle it. For small sailboats, the tiller pilot guide is a good first read, and for boats with hydraulic steering, the hydraulic autopilot guide matches the drive form to the steering.

Budgeting against your boat's power supply

A power budget is a list of the loads your boat's electrical system carries while you run: navigation lights, radio, instruments, the autopilot. To budget, you compare those loads against what the batteries and the charging source can supply. The maker's page for your battery is the place to read its voltage and capacity. No article can give you a universal figure, because every boat's loads differ.

The operator keeps the watch even when the autopilot steers. The U.S. Coast Guard Boating Safety page is a general source for boating safety and education, and it is worth a visit when you plan a season's use. The autopilot is a steering aid, not a lookout.

Longer passages ask more of the electrical system. The questions to plan around are: how long you run between charges, what else is on the same circuit, and whether the charging source keeps up. Those answers come from your own boat, not from a listing. General guidance on the supply side lives in the power supply article, and planning the whole install is covered in the installation planning article.

12-volt and 24-volt as words on a listing

Listings name voltage in different ways. A pack page may say 12-volt, or a range such as 12-24 VDC, as the NavPilot 300 page does. The boat's own system is usually 12-volt or 24-volt. Before you choose, read the stated voltage and ask the dealer what the pack expects.

Voltage is a matter of matching, not of more being better. A pack that states a range covers both systems, while a page that states a single voltage names the one it expects. The 12-volt versus 24-volt article and the voltage system article explain how those words read on a listing.

Questions to ask the maker, the dealer and the installer

Once a listing has narrowed the choices by stated details, the next questions belong to the maker's page and a qualified installer, not to a buying guide. The autopilot's own manual is the source for the supply wiring, and the dealer can confirm what a pack expects.

• What voltage does the pack expect, and does the boat's system match?
• What wire size does the maker's page specify for the power feed?
• Is a fuse or breaker called for at the supply?
• Where will the installer place the course computer and the drive?
• Does the pack state a separate rudder reference, or is it built in?

What to pick for your situation

Questions

Does a listing give the power draw in amps?

Usually not. Listings name the parts and often state the voltage, such as 12-volt or 12-24 VDC, but the amperage is a detail for the maker's page and the maker's manual. This site compares stated details only.

Do larger drives use more power?

A drive that does more work on a heavier steering system will have a more demanding supply requirement, but there is no general figure that applies to every boat. The maker's stated details for the specific drive are the source, and a qualified installer can match the supply.

Is a 12-volt autopilot enough for my boat?

That depends on the boat's own electrical system. Read the voltage stated on the listing and the maker's page, then confirm with the dealer whether the pack expects 12-volt or a range such as 12-24 VDC.

Do I need a dedicated battery for the autopilot?

That is an installation question for the maker's manual and a qualified installer. The right answer depends on your boat's loads and charging, not on a listing, and no article can promise one configuration for every boat.

What if a listing does not state voltage?

Ask the seller for the maker's page, or look the model up on the maker's site. Voltage is a stated detail you want before you choose, because it has to match the boat's system.