You have a friend working at [insert here the name of a company], and he recommends you a product made by them. Say a radar, or an autopilot. You read the specifications and find out that the product is designed for boats up to 60 feet; and yours, lucky you, is a 30 meters. What should you do?

We all know how an autopilot works:

  • The boat moves (of course!): yawning, pitching and rolling make her deviate from her course
  • The autopilot is connected to any device which may measure such deviations: compass, gyro, GPS, tachometer…
  • The autopilot gets as well, as an input, the intended track to be followed
  • The autopilot has a computer in it, which calculates (with all the data input) how the rudder blade has to be moved in order to keep course
  • The autopilot reacts after these calculations, sending a signal to the hydraulic pump which makes the steering gear move

So the rudder is moved by the steering gear, which is moved by the hydraulic pump; this pump gets instructions from the computer in the autopilot (the brain). But what would happen if the pump didn’t have the capacity to cope with all the orders it gets? This may happen if the rudder has to react too often, or too fast, or for too long; or if the boat is too big.

Autopilot set from Garmin: display, computer, electronic control unit, cables

Perhaps you can relate: in bad seas the autopilot gets stuck because the boat moves too much, and the capacity of the hydraulic pump is not enough to cope with that much job. That is why it’s so important to know which equipment we have to install on board: one for a pleasure boat is different from one for a work boat (i.e. heavy duty); one for a day cruise is different from one for a transat crossing.

Hydraulic installation of an autopilot. Source: Garmin

A general advice is to follow the recommendations of the maker: it is for a good reason if he says that the autopilot is for 60 feet sail boats… When choosing an autopilot, you have to take into account where and how you will use it:

  • Motor or sail boat
  • Measures of the boat (length and displacement)
  • Planning or displacement hull
  • Installation at the cockpit (more simple, less expensive, but easier to get any component damaged by water, salt, corrosion, etc.)
  • Installation below deck (more expensive, but far better in terms of quality and reliability)
  • Hours of use, both in general (in a year, for instance) and in continuous service (two hours to reach your favourite beach; or a week to get to Bahamas)
  • Integration with the rest of the equipment on board (GPS, radar, electronic charts, etc.)

You will have to decide as well what will you use it for: racing, fishing, short trips at 40 knots…? And of course you will need the autopilot to work fine in tough conditions, when you may need both hands for other things, far from the steer. That is why it’s important not to fall short when choosing a model, mainly when it comes to the hydraulic pump. If you choose one not suitable for your boat, it will probably struggle when you force a continuous work in rough seas out of it.

Moreover, the electronic equipment (and the electrical one, if the steering is electrically geared) must have a suitable capacity: both the circuit feeding the steering gear and the processor of the autopilot need higher power and more electrical current as the service grows more demanding. That part of the autopilot can fail as well, if the model is too small.

Do you want to install an autopilot, but you still have some doubts? Contact us and we’ll be delighted to help you!