Need a new autopilot? Peter and Cheryl Ainsworth share their experience step-by-step as they re-fit their 1989 Hylas 47 yacht.

All of the installations and maintenance on board are undertaken by Peter, keeping costs down and ensuring a good understanding of how everything operates. A solution will always become apparent to what may seem an insurmountable problem — sometimes sooner than later! Necessity is the mother of invention, as they say.

Without a doubt, autopilots are a necessary item on board, especially if you are sailing off over the horizon. Installing a below-deck autopilot can be a daunting experience, both in terms of choosing one and deciding where and how to install it on your yacht.

Needing a below-deck pilot before crossing the Pacific Ocean, we had the added complication of undertaking this in Central America, in far from ideal conditions, during summer with temperatures around 40 degrees Celsius. After all, what is cruising about . . . ? Yes, boat maintenance in exotic locations!

Fortunately for cruisers today, internet access is available in the most unlikely places, enabling us to at least get to first base, researching the model and make to suit our individual requirements. This can also be overwhelming because there are so many products to choose from and so much information documented about various autopilots. Cruiser forums offer excellent support from those who have gone down a similar path and wish to share their experiences. Because our yacht has only a wheel pilot and never had a below-deck autopilot installed, we had to start from scratch.

What type?

For us, our decision was based on availability, cost, the ease of interface with other instruments we had recently purchased and our requirement of bluewater cruising. The best advice we had from fellow cruisers about choosing an autopilot was that whatever the make, always choose a more powerful unit than what the manufacturers recommend, to assist in the unlikely event of being caught out in gale-force conditions. Perhaps it’s more of a case of peace of mind than an actual requirement, but it sounded like a good idea to us! Although we already have a wheel pilot which will remain installed (the same model we had on our previous yacht) we know from experience that in heavy conditions, especially with cross-seas, it is not reliable.

We opted for a Raymarine SPX-30 Smart Pilot Unit with an Octopus Hydraulic 12-inch linear drive ram. The Raymarine components cost us a total of US$3585, with the Octopus Ram another US$1230. Additional costs included $150 for fabrication of mounts and another $100 for installation materials. Costs will vary where you buy yours — we purchased ours in the US because we were in Mexico. Whatever brand you buy should obviously have a good reputation for warranty and servicing/parts in the area you plan to cruise.


Installation can be done either in or out of the water. Because we were already hauled out, the installation was completed on the hardstand, with some degree of confidence that all would work well when we were floating again. Even though we had installed a similar pilot on our previous yacht some five years ago, each yacht is very different, so for most of this, we were back to square one; working through the process carefully. We still found the most difficult part of the installation deciding where the component parts were to be located on the boat.

There are seven essential component parts of the autopilot installation: the electronic compass, computer unit, rudder angle reference unit, hydraulic ram, hydraulic motor and pipes, cables and the control head.

Careful consideration was needed for the location of the electronic compass because the manufacturer provides guidelines requiring it to be placed on a null point in the yacht. In our previous installation, the control head repeatedly came up with an error because we had stored some cans in a nearby locker. Although finding a null point on a yacht can be very difficult, it is crucial to the successful operation of your autopilot. One way of doing this is by using a handheld compass to find a place where the compass point does not deviate from a known direction.

The rudder angle reference unit is located near the quadrant. Its function is to supply the computer with information as to which way the rudder is actually facing. This unit was mounted on a bracket made from ply and timber, glued and screwed to an adjacent bulkhead and connected to the rudder quadrant with the supplied piece of threaded rod and mounting hardware.

The computer unit requires its mounting to be somewhere dry, central and accessible, not using up valuable space, keeping in mind how much cable you have to connect it to the hydraulic ram. Somewhere in the middle of the yacht is usually a good place.

For us, one of the most difficult decisions was how to attach the hydraulic ram to both the quadrant and the hull. There was not enough space to have a separate quadrant made for the ram. The position of mounting the hydraulic ram to the hull is also crucial because it needs to be on the same plain as the quadrant. Because we did not want to lose any valuable locker space, we opted to attach the hydraulic drive to the existing steering quadrant, engineered locally (in Mexico) from stainless steel, bolted to the quadrant. (This is illustrated in the step-by-step photos.) In addition to this, a right-angled bracket was also engineered to mount the other end of hydraulic drive to the yacht. In order to do this, the flow coat from the inside of the hull in the area the block was to be bonded had to be ground to a clean surface. Once this was done, the specially fashioned cedar block (2.5cm x 8cm x 12cm) could be glued and glassed in position. All the outside edges of the block had to have a soft edge put on them so as to enable the glass cloth to drape over the timber. A blend of epoxy resin and glue powder was mixed to a slightly stiffer than mayonnaise consistency before being applied. Dive weights came in handy to hold the block in place while the glue dried. For all glassing, three layers of 10oz double-biased glass cloth were cut and applied with epoxy resin. Due to the high ambient temperature of our location we used ultra-slow hardener. Even using this, there was still a very short working time with the resin.

The mounting of the hydraulic motor is determined by the space available and its flexible pipe work and obviously needs to be located somewhere near the hydraulic ram. For this a bracket was also made out of plywood and timber, glued and screwed to a nearby strong bulkhead.


There are a myriad of cables that need to be sorted. Running of all power cables has to be from a reliable source. When connecting the power cable to the hydraulic motor, one idea is to do so with a terminal block for ease of removal and inspection if necessary. There is an interface cable from the wind instruments to the computer unit and three cables that run from the computer unit to the steering area (main power, rudder reference cable and motor clutch cable). Once you have decided where the component parts are going to be installed, the cables can be run to check that you do in fact have the correct length of cabling to do the job.

Lastly, the control head is required to be installed in a convenient location near the wheel. We designed and made our own pod out of glassed plywood which was then faired and coated with appliance white spray paint.

Before installing all the components, all exposed edges of fibreglass, plywood and timber were given a coat of white two-pack urethane for both protective and decorative purposes.

The hydraulic drive can now be bolted to its mounting and the rudder reference unit screwed to its mount, following drawings supplied by the manufacturer. The hydraulic motor can be bolted into place, allowing pipes and clutch cable to be attached. Any remaining cables, previously run, can now be attached.

Commissioning and sea trials

You are now ready to commission and sea trial your installation. The manufacturer’s manual should have the details for this. It is important to make sure that the rudder turns the right direction, using the control head. If it does not, one solution is to check that you have the wiring polarity correct. The rudder reference unit needs to be tuned to the yacht by adjusting the length of the threaded rod which connects the two together. The yacht rudder needs to be in the middle when the control head indicates it is in the middle.

During sea trials, small modifications (hopefully!) can be made as required.

Seven steps

There were basically seven steps we followed in the installation of our autopilot unit. (This was completed with continual reference to our specific manual.)

1. Decide positioning of components within boat

The ram, motor, and rudder reference unit are located under the floor of the lazarette locker, while the computer unit and electronic compass are located aft of the engine in a void space beside some drawers.

2. Organise any engineering and fabricating of mounts

The photographs with this article show the modifications to the steering quadrant, cedar block before and after glassing (note the flow coat has been ground underneath the cedar block), the mounts for the rudder reference unit and the hydraulic pump which Peter later painted. They may look a little agricultural, but they work! The fabrication of the steering quadrant can be seen with the quadrant in place. Making a specific pod to mount the control head enabled a nice neat fitting.

3. Install components

The computer unit, compass and control head were installed first, with the cables run to the aft locker to check for length. Finally each component was mounted up aft. The cedar block provided an excellent mount for the ram.

4. Run the cables

Run all the cables, ensuring that they are supported by suitable cable mounts every 30cm.

5. Connect the cables

Connect all cables following the instructions in the manual.

6. Commission

The commissioning of the autopilot involves two stages. Firstly there is a process carried out with the boat not moving (i.e. on the hardstand or in a pen). The second process requires sea trials. That is, the boat is now moving. All manuals for all autopilots go into the commissioning process in great detail and it would be very wise to follow these instructions carefully.

7. Sea trials

These enable the autopilot to understand the vessel. For example, whether the vessel responds quickly or slowly to various amounts of applied helm. Also in the sea trials the compass is corrected by turning the boat in various circles. During this process, our specific Ray Marine pilot “learned” about our boat’s manoeuvrability. This is a kind of “fuzzy logic”.

Proof of the pudding

Some of our re-fit was undertaken as we sailed south towards El Salvador. This enabled us to get the necessary engineering and other bits and pieces where we could. But most of all, it enabled us to get out there and enjoy our boat. Raymarine America thought that our installation was excellent, which will be a comfortable thought when we are in the middle of the Pacific Ocean.

comments powered by Disqus