The essentials in 30 seconds
- The choice is made on loaded displacement, not length. Manufacturer charts speak in tonnes: mechanical linear drives cover from ~11 t (Raymarine Type 1) to ~35 t (Garmin Type 3) depending on the model.
- Electromechanical linear: one box, simple installation, the default cruising choice. Hydraulic: pump + cylinder (or integrated rams like B&G T1/T2), with a perfectly free helm when disengaged thanks to the bypass — the argument for racing programmes and rotating crews.
- Reversibility is not "locked" versus "free": a clutched mechanical linear drive also frees the helm when the pilot is off — with residual linkage friction that a bypassed hydraulic does not have.
- Up-to-date budgets and prices live in the autopilot comparison page — this article focuses on the technology; labour is the real variable: ~4-8 h for a linear drive, 8-16 h for a full hydraulic run.
Contents
The steering drive is the autopilot's muscle: it turns an electrical order into rudder movement. Two families coexist — electromechanical (motor + screw) and hydraulic (pump + cylinder) — and the choice shapes ten years of use. For maintaining an existing ram, see our maintenance guide; for the complete system, see B&G vs Raymarine. Here we only discuss drive technology.
The two families
Electromechanical linear. An electric motor turns a screw that pushes a rod linked to the quadrant or rudder stock, with an electromagnetic clutch in between. Everything lives in one housing: a finished product, bolted on and forgotten. It has been the mainstream leisure technology since the 1980s — joined this month by the brushless built-in-ECU generation, see the Garmin SmartDrive announced September 1st.
Hydraulic. An electric pump feeds a cylinder attached to the quadrant. Watch the delivered scope — this is where budgets go wrong: some references are complete rams (pump and cylinder integrated in one body, e.g. B&G T1/T2, Lecomble & Schmitt LS40ST), others are a pump alone that assumes a cylinder on board (e.g. Garmin SmartPump v2, for boats with hydraulic steering). A pump's list price never represents the installed system.
Six criteria that decide the choice
1. Thrust and sizing. Size on loaded displacement (water, fuel, crew, gear — often +20-25 % over the builder's figure), following the manufacturer's chart rather than a universal rule. Current manufacturer references: Raymarine Type 1 = 295 kg thrust for ≤ 11 t; Garmin Type 1 = 400 kg for ≤ 13 t; Garmin Type 2 = 730 kg for ≤ 21 t; Garmin Type 3 = 1,080 kg for ≤ 35 t. For racing or steep seas, take the category above your loaded displacement.
2. Rudder speed. Hard-over time (±35°) measures responsiveness. Observed orders of magnitude: 10-15 s for a cruising linear drive, 8-12 s for a well-sized hydraulic, 5-8 s for racing setups (fast pumps, direct drive) — at the cost of higher peak draw. Faster than that, you break gear or drain the bank.
3. Power draw. The pilot is one of the top items of the 24 h energy budget (see battery bank sizing). A linear drive draws ~1-3 A in cruising corrections; a hydraulic pump 3-8 A in peaks but over shorter cycles: over 24 h in a seaway the two technologies come out close. Brushless (SmartDrive) claims lower averages — to be verified over a season.
4. Reversibility. Often told wrong: a clutched mechanical linear drive frees the helm when the pilot is disengaged — it does not "hold" the rudder. What remains is residual friction from rod and linkage. A bypassed hydraulic does better: valves open, the helm is perfectly transparent. That helm feel — more than raw "freedom" — is why crews that hand-steer a lot prefer hydraulics.
5. Maintenance and lifespan. No decisive gap if the installation is right: seasonal greasing and play checks on the mechanical side; oil level, condition and tightness on the hydraulic side, with periodic fluid changes. Details in the maintenance guide.
6. Footprint and installation. Linear: one housing between structure and quadrant, ~4-8 workshop hours. Pump + cylinder hydraulics: two units, high-pressure hoses, bleeding — ~8-16 h. Integrated hydraulic rams (T1/T2, LS40ST) install almost like a linear drive.
Electromechanical drives — figures and brands
Garmin — Type 1 and Type 2 linear drives (Type 1, Type 2): driven today by the Reactor 40 course computer with the GHC 50 instrument. Type 1 for ≤ 13 t, Type 2 for ≤ 21 t (manufacturer chart). And since September 1st, the brushless built-in-ECU SmartDrive (≤ 15 t) is the brand's integrated entry point.
Raymarine — Type 1/2/3: the historic Evolution range. Type 1 (295 kg, ≤ 11 t, 300 mm stroke) with ACU-200; Type 2 and 3 with ACU-400. Computers and accessories distributed by Skysat; drives sourced per configuration. Note: the EV-100 (tiller/cockpit wheel) cannot drive these inboard rams — an EV-200 pack minimum is required.
Hydraulic drives — figures and brands
B&G T1 12 V / T2 24 V (T1, T2): integrated hydraulic rams (pump + cylinder + bypass in one body), driven by the NAC-3 computer. The offshore sweet spot once loaded displacement exceeds what a linear drive handles serenely.
Lecomble & Schmitt: the French manufacturer (LS40ST / Newave range, integrated electric bypass), factory-fitted on many Bénéteau and Jeanneau — hence its refit appeal: replace like-for-like without rethinking the layout. Sourced on project request.
Simrad DD15 (direct drive unit): a case of its own — direct drive on the rudder stock, electric, 12 kg, rated by Simrad for sailboats between 30 and 45 ft. Full reversibility, immediate response, contained draw: the regatta choice in that size, provided you accept a boat-specific mechanical integration on the rudder axis (parts and labour quoted separately).
Garmin SmartPump v2 (product page): a reversible pump alone, designed for boats already fitted with hydraulic steering — it ties into the existing circuit, driven by a hydraulic Reactor 40. On a cable-steered sailboat with no hydraulics, an integrated T1/T2 ram is almost always simpler and cheaper at system level.
Table by displacement and programme
| Loaded displacement | Programme | Recommended technology | Typical references | Thrust reference |
|---|---|---|---|---|
| ≤ 7 t | Coastal, summer weeks | Electromechanical linear (or SmartDrive) | Raymarine Type 1, Garmin Type 1, SmartDrive | 295-475 kg |
| 7-13 t | Offshore cruising | Linear Type 1/2 — integrated hydraulic if steep seas are frequent | Garmin Type 1/2, B&G T1 | 400-730 kg |
| 13-21 t | Offshore, transat | Integrated hydraulic or linear Type 2/3 | B&G T2 24 V, Garmin Type 2/3, L&S | 730 kg-1 t |
| ≥ 21 t | Bluewater, yachts | Project-sized pump + cylinder hydraulics | Garmin Type 3, custom L&S, SmartPump v2 if hydraulic steering exists | ≥ 1 t |
| 30-45 ft | Racing, regattas | Direct drive or fast hydraulics + racing controller | Simrad DD15, L&S pumps, Madintec MAD Controller | per config |
Up-to-date pricing for each configuration lives in the autopilot comparison page — deliberately not here: prices move, articles stay.
Examples: 35 / 45 / 55 ft
35 ft / ~6.5 t loaded — coastal plus occasional offshore. Type 1 linear drive (Raymarine or Garmin depending on the boat's ecosystem), or SmartDrive for the latest Garmin integration. Matching computer (ACU-200 or Reactor 40), ~8 h installation.
45 ft / ~11 t loaded — offshore + transat. Our workshop pick: integrated hydraulic B&G T1 + NAC-3 + Precision 9 + RF25N — for the helm feel when disengaged (rotating crew) and the margin in a seaway. ~12 h installation.
55 ft / ~16 t loaded — fast cruiser-racer. Project configuration: fast hydraulics or direct drive depending on the rudder axis, racing controller (Madintec on top of a NAC-3). At this size, sizing is done on deck plans and on-board measurements — not a generic table.
5 mistakes seen at the workshop
1. Sizing on the builder's displacement. The "7.5 t" boat sails at 9.5 t loaded. The drive works at its limit, heats, ages fast. Always the loaded displacement.
2. The "economical" linear drive on a 15 m offshore boat. In a seaway the ram saturates, the pilot drops off, and the saving is paid back in hand-steering watches. Thrust margin is not a luxury; it is the product.
3. Hydraulics without a bypass. On old or second-hand kits, check for the bypass valve: without it, the helm stays braked with the pilot off. Modern pilot rams build it in.
4. Mixing ecosystems unknowingly. Raymarine plotter + Garmin pilot = two interfaces ignoring each other. Match the pilot to the main plotter's ecosystem — or use an open controller like Madintec.
5. Mismatched pump and cylinder. Pump flow unsuited to cylinder volume = steering too slow or too brutal. Pair elements validated together, by the manufacturer or the installer.
FAQ — Choosing your sailboat drive
Can an existing electromechanical system be converted to hydraulic?
Yes, but it is a heavy job: hydraulic cylinder, pump, high-pressure hose runs, bleeding, and often a quadrant adaptation. Count on a substantial workshop intervention. It makes sense when the boat's programme genuinely changes — committed offshore sailing or racing — not for a marginal gain.
My sailboat already has a Lecomble & Schmitt ram; can I drive it with a Garmin or B&G computer?
In most cases, yes. L&S rams are hydraulic cylinders with an integrated electric bypass: a third-party course computer can drive them if its power output and bypass control match (voltage, max current, rudder feedback type). It is an interface check done on the datasheets before ordering, not a gamble. Madintec's MAD Controller is designed to interface with most drives on the market.
What is the difference between reversible and non-reversible hydraulics?
A reversible system leaves the helm free when the pilot is disengaged — thanks to a bypass valve (built into modern pilot rams) that connects the two cylinder chambers. A non-reversible system locks the helm as soon as the pump stops: that is how a classic hydraulic wheel-steering circuit behaves, not what you want from a pilot ram on a sailboat. On recent pilot rams (B&G T1/T2, L&S) the bypass is built in; check for it on old or second-hand kits.
Is a steering ram compatible with a quadrant?
Yes in nearly all leisure configurations. The ram acts on the quadrant or rudder stock through a clevis. Compatibility comes down to quadrant rotation angle (typically ±35°), ram stroke and available space — an on-board measurement before purchase avoids bad surprises.
Should you carry a spare drive offshore?
Not a spare drive: a fallback strategy. A windvane (Hydrovane, Windpilot) or emergency tiller for sailing, and above all a removable pin between ram and quadrant so the helm can be freed if the drive ever jams. See our maintenance guide for early warning signs.
What wiring between the course computer and the drive?
Gauge calculated on the drive's maximum current with margin — in practice 2 × 4 mm² for a small linear drive over a few metres, 2 × 6 mm² beyond, up to 2 × 10 mm² for powerful pumps over long runs. Fuse protection sized per the manufacturer's manual, reachable at sea. The exact calculation depends on the round-trip length: we validate it at quote stage.
