Installing Our Garmin GHP 10 Autopilot

Chuck at the helmAfter 17 years of sailing on our Mariner 40 Ketch, Sea Trek, we were really used to having an autopilot do most of the steering for us. With Beach House, we did all of the steering ourselves, until now. Both the trip from South Carolina to the Chesapeake and the return to Florida required us to steer every foot of the way. We often mentioned on those trips how much we would like to have had some electronic help. An autopilot has always been on our to-do list, but we decided to wait and install the latest model just before departure time on our upcoming cruise. The time is now.


display head locationThe first step in any installation is to decide where all of the bits and pieces are going to go. Our first and easiest decision was where to mount the GHC 10 interface control head. We wanted it in the flybridge since that’s where we do most of our steering. We only use the lower helm in bad weather. This was also the reason we decided not to install a second control head at the lower helm. Well, that and the fact that we are running out of real estate.

autopilot remoteFor the lower helm, we decided to use a remote for the occasions when we would be steering inside. The Garmin remote was a perfect fit and we could use it in any location on the boat. We often sit on the bow while underway with the autopilot steering the boat.

Display cut outThe provided template for the GHC 10 has a sticky back so it was attached and lined up properly exactly where we wanted it. We needed a spot near the helm but with at least 3-inch clearance behind it to allow for the cabling. The GHC 10 must be connected to the NEMA 2000 network. There are also 2 wires that must be connected to the course compute unit (CCU) and the electronic control unit (ECU) interconnect cable.

wire runTo accomplish that, a wire run from the flybridge to the area behind the lower helm was needed. Beach House is fairly easy to make long wire runs without drilling holes all over the boat. The flybridge wiring and hydraulic tubing provides easy access.

fluxgate compassThe CCU acts as the brain of the autopilot and contains the sensory equipment to determine heading. We often referred to this in the past as a fluxgate or gyro compass. It’s much more sophisticated in the Garmin. The unit has to be mounted in the front half of the boat and as low as possible. Garmin instructions say that it should not be mounted any higher than 10 feet above the waterline. We mounted it in a forward locker under the V-berth. It would be below the waterline in this spot. Another important factor is that it must be free of any magnetic influences, especially any metal objects. Also, it comes with its own nifty mounting bracket.

helm pumpOur hydraulic steering system is fed by copper tubing throughout. This would not work to connect the autopilot pump into the lower steering station. We chose this location for our ability to connect the pumps easily and not have to re-plumb the entire system. The autopilot pump must be mounted within 18 inches of the course computer, so the location also allowed us to mount all of the additional parts in one location.

hydraulic lineWe found all of the necessary Teleflex tubing and connections at a local NAPA store. None of the marine suppliers in Naples or Marco Island could provide us with what we needed. Go figure. We also purchased hydraulic fluid so we could bleed the system once everything was installed. This flexible tubing made the replacement process much easier and quicker than trying to work with the copper tubing. The Teleflex fittings were all quick connects, and since I had used them many times in the past, I knew that if they were installed properly, they would not leak.

connecting new linesThe new lines were attached to the helm pump and then secured to the bulkhead so they wouldn’t move around. It required a port and starboard line as well as a return line. The copper return line from the upper helm was left in place.

shadow driveThe Garmin GHP 10 contains a patented “Shadow Drive” that allows the helmsman to take over the steering by simply turning the wheel. This disengages the autopilot and allows you to steer the boat until you want the autopilot to take over again by steering a straight course. The Shadow Drive needs to be plumbed into either the port or starboard hydraulic line. It has to be mounted horizontally as level as possible and closer to the helm than the autopilot pump. It’s important to secure it to the bulkhead to prevent it from moving around. It, too, must be mounted away from any magnetic influences. Since we have dual helms, the drive has to be mounted between the autopilot pump and the lower helm.

autopilot pumpThe next step is to install the autopilot pump itself. The pump size is determined by the specifics of the boat and we chose the 2.0 litre. They come in several sizes. Our pump is mounted on a flat surface directly under the lower helm.

autopilit pump installedThe ECU unit is mounted to the bulkhead just above and to the right of the pump. They need to be mounted within 18 inches of each other. The pump is connected to the ECU via the supplied cables.

wiring diagramThe Garmin GHP 10 is completely NEMA 2000 and it makes the installation almost plug and play. There are a few cautions - the NEMA 200 connections must be made with the proper orientation of the fittings for the backbone and cable runs. Once the autopilot is installed, we now have the beginnings of a NEMA 2000 system and can easily add additional equipment later. The final connections were the NEMA 0183 output from our Standard Horizon chartplotter so the autopilot would have heading and speed information. With the autopilot set up this way, we did not need a rudder sensor. The Garmin calculates the rudder position based on the number of turns stop to stop and other factors during the calibration process.

autopilot layoutWhen everything was installed, it looked very close to the layout provided in the installation instructions. The only thing left was to bleed the hydraulic lines and go through the calibration process. But one minor issue had to be dealt with first.

upper helm removedWe had a slight leak in the upper helm pump so it was removed and sent off to have the seals replaced. This would be the second time we have had to replace seals in the upper helm. This time we hope it lasts.

upper helm paintedBefore reinstalling it, we gave it a fresh coat of paint so it looked nice like the rest of the flybridge. After 30 years, it was looking a little ragged.

upper helm reinstalledIt all went back together and the hydraulic lines were reconnected. Things were really looking good at this point, and it is surprising how easy the installation went considering the need to change so much of the system.

upper steering
With the wheel back on, the entire system was bled and everything checked for leaks. All went well and the calibration was the next step. Part of the calibration is done at the dock and part is done underway. The sea trial, and the entire process for that matter, is done via the calibration wizard within the autopilot. It really is very simple, but we must look a little crazy out driving the boat around in circles and letting it drive in an S pattern. Once the installation was completed, we were very happy to welcome our newest crew member aboard, the autopilot. It really is like having a third person on board.
Next comes the generator. Stay tuned for that installment.
display finished


  1. Thanks for the write-up. I am looking at installing exactly the same system, and I now officially feel slightly less intimidated by the process. :-)

    1. Your very welcome and good luck with the install.

    2. Hi Chuck,
      I have read many of your articles in the past, and now I am also seriously considering installing a auto pilot in my bayliner 3788 with twin cummins diesels. I have had many boats over the years but have to admit I am a little nervous about taking on the ap installation. My boat has hynautic three line system , but the tubing leaves the helm area and does not show up again until it appears in the cockpit area where it is connected to the sump and the steering ram. there is plenty of room for the pump near the ram and the ccu can be installed there to I guess. If I install the shadow unit under the bridge helm, I guess I am free to install the new pump unit near the ram. My ram is a 10.2 cu in and I am thinking about buying the garmin 2.1 pump. Any suggestions would really be appreciated as I am shopping around now for the best price on the garmin 10 and the 2.2 liter pump. Bill dieffenbach

    3. Bill, I don't see a problem with your installation. I would suggest you go to Garmin's site and download all the installation instructions. There is a limitation on how far some of the components can be from each other and the cable runs, so check all of that even before you decide to buy. It might be better if you can do as we did and plumb the pump near the helm. It's pretty easy to make all the connections at the helm pump, including the drive pump. The N2K cabling is easy and you will probably need some additional cables, they never give you the right lengths. Lay it all out on paper and compare that to the installation instructions. Figuring the hydraulic connections and additional tubing takes some planning, but it's not a big deal and you can make changes as you go along without any major problems. The pump just connects to the port, starboard and return line in the steering. Good luck.

  2. Chuck,

    Great article as always. I'm working my way through your project write-ups as we resurrect our 68 GB. Unfortunately (?) we have a cable and pulley steering system in lieu of a hydro. Any suggestions on an autopilot system? There is an ancient rotary switch on our lower helm and I found an abandoned box inside the flybridge that seemed to go with it. No info seems to be available, plus I'd rather run my own so I understand it all. Any suggestions would be greatly appreciated. Thanks!

    1. Randy, I haven't worked on a cable steering unit for quite some time. You do have a few options. One would be the Garmin GHP 12 with an Octopus drive. You may check to see what drive Garmin recommends. The Simrad AP24 is also used for cable steering and I have always had good results with Simrad. We considered the Simrad when we installed ours originally, There is also a Canadian company called Comnav that makes an excellent unit but it does not have a lot of bells and whistles. Good luck.


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