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3870 Steering ram size-gctid359633

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    3870 Steering ram size-gctid359633

    I am installing a GHP 10 Garmin auto pilot on a 1986 3870. Trying to determine what size pump, to purchase and if the steering system is balanced or unbalanced. I need to have the cubic inches of the steering ram.

    I have herd of installing a larger pump than the spec, pump. Pros or cons?


    I am also thinking about installing auto pilot Navman 3380 on my 1990, 3888.

    So I also need to have the cubic inches of the steering ram-cylinder..

    Please help !

    1990, 3888 Motoryacht
    "Disco Volante"
    Marina Cervar - Croatia


      The GHP 10 was a wonderful addition to our 1988 3818. We love it and would not be without it. It works VERY well. We are living on the boat 3 weeks out of 4 and have completed 1/2 of America's Great Loop.

      The auto pilot was and is very useful. It gives the helmsman a break from steering. It allows you to drive the boat even in the ROUGHEST conditions without wearing out your arms. We used it to do the 90 mile crossing of upper Lake Michigan in 3-4 ' beam seas. it was a wonderful. Surprisingly; we found it very helpful on America's Rivers because heading hold keeps the boat on a heading leaving the helmsman free to stand up and maintain a better watch in from of the vessel for debris, markers etc. etc.

      Your Hynautic steering cylinder is balanced. I believe that the displacement in 9 CID.

      Choose the smaller pump. Initially I installed the mid sized pump and had to replace it after one year of frustration, trying to calibrate the pilot.

      I believe that I was the first to install a GHP 10 on an old Bayliner with Hynautic steering. The difficult part was getting accurate information. Once I had assempled the information, the rest was not too difficult. I did a huge amount of reading and research before I even started the install to make CERTAIN that everything was done according to Garmin's recommendations.

      I did the entire installation myself

      I can tell you where I mounted the CCU, GHC10, Shadow Drive, ECU & pump. I can also send you photos of the completed installation.

      Call me on Skype and I will share my observations with you.

      Just give me a time when I should be online. I am in Toronto Eastern Daylight Time


      cell 416 570-4957


        A balanced system means that the same volume of oil is required to move the cylinder in either direction.

        The cylinder stem will protrude from either end of the cylinder.

        The space or volume on either side of the pison is equal.

        The helm pump volume is the same in either turning direction, regardless.

        Of course the diameter of the cylinder (volume/cu in) determines the work load that it's capable of.... also controls the speed in which the cylinder will move per helm pump volume.

        The cylinder p/n should get you the cu in info necessary.

        Example photos of balanced system cylinder.

        Unbalance system cylinder.

        Rick E. (aka RicardoMarine) Gresham, Oregon
        2850 Bounty Sedan Flybridge model
        Twin 280 HP 5.7's w/ Closed Cooling
        Volvo Penta DuoProp Drives
        Kohler 4 CZ Gen Set

        Please, no PMs. Ask your questions on forum.


          I have also installed the GHP-10 and LOVE IT. My cyclinder is unballanced unlike the pictures above, I only have 1 piston running the strb rudder with a arm to the port rudder I have an 85 3870 don't know if they changed the steering system. I bought the 2.1 ltr pump and it responds well, you can tune down the rate that it corrects. I also bought the remote for it so I can steer from anywhere in the boat $275 for the remote and well worth it IMO. Can fish and troll steering from the aft deck.........You can also call Garmin Tec support these guys are great, follow the instructions to set it up. It took a full weekend for my brother and I to install then another day to test run and set up.


            You probably have a K19 Hynautic and H50 Helm. Should be a mark on the gold colored end. Spec says 8.3 cu in. Here is link to spec sheets

            Good luck - a good autopilot makes boating a lot more relaxing. The Garmin is a great choice - I wish I would have made the same choice...the Comnav system I got talked into is a real "@#[email protected]" and I wouldn't recommend it to anyone...I cuss it every trip out.


              Mike, maybe I misunderstood you..... but the difference is that the balanced cylinder stem (aka rod or piston rod) protrudes at either end of the cylinder body..... whereas the unbalanced protrudes at one end only. Either type of these cylinders have a single piston.

              This single piston cylinder would be an unbalanced cylinder if it was a marine steering cylinder.

              It could just as easily be a single piston balanced cylinder if the stem also protruded through the base end.

              Rick E. (aka RicardoMarine) Gresham, Oregon
              2850 Bounty Sedan Flybridge model
              Twin 280 HP 5.7's w/ Closed Cooling
              Volvo Penta DuoProp Drives
              Kohler 4 CZ Gen Set

              Please, no PMs. Ask your questions on forum.


                I agree with post # 6 from Sea King


                  I just installed the GHP10 on my 3870. I learned a lot and would be willing to consult with anyone if they have any questions on that specific install.

                  Only used it once so far while calibrating and I am already asking myself why I didn't have one sooner!


                    Rick: You are right. Maybe I wasn't clear, my steering cyclinder only protrudes at 1 end so It is a unballanced cyclinder.


                      Oh thanks a lot. I have been putting off getting an auto pilot on my 3870 for years. Now I am going to have to do it. Just when I had convinced the wife that I wasn't going to spend big bucks on the boat this year.

                      You guys keep getting me in trouble.

                      PS: The system on my 3870 is a Wagner with a balanced cylinder


                        SEA KING thank you for posting the specs on the K-19 steering ram, with 8.3 cu".

                        As i understand the system is unbalanced.

                        I have purchased the 2.1 L thinking the cu were larger. Garmin web site specs are for the smaller version 1.2 L with an Unbalanced kit.

                        I think going with the larger 2.1 (were i can change the flow rate) was a better way to go in the end. It comes with the valves for either balanced or unbalanced. I see others have installed the 2.1L with success on their 3870. So i'll post when its all done and working.

                        First of all i'm a big GARMIN fan. Great products, wonderful FREE updates, and good tech support. Plus they are always leading the industry in quality and innovation. Like and i-product for the marine industry. After reviewing many other products and costs. It came down to a no-brainer for me. GHP-10!

                        Now i'm looking to where i can mount the head unit? In the 3870 lower helm? I'm going to have to bite the bullet and upgrade the rest of the electronics. I'm just waiting on this rebuild on my EH700 to be done and behind me before i part with the $$$.

                        for what its worth.


                          I had considerable difficulty sorting inconsistencies between Garmin and Hynautic when I installed our GHP10.

                          Note that I originally set my system up based on information that the steering ram was un balananced (WRONG). Then; I ordered & installed my system with an unbalanced valve and installed the system with a 2.0 liter pump (WRONG AGAIN). To further complicate the job and to add to my misery & FRUSTRATION; the recommended hydraulic installation & configuration that Garmin had posted in their FAQ website was also WRONG.

                          Note that my system works perfectly now. It is now set up as a balanced steering system with a 1.2 liter pump

                          Here below is a series of email between myself and a support person at Teleflex in Richmond BC. Teleflex purchased the assets of Hynautic. This was the start of me getting the CORRECT information.

                          ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++++++++++++++++++

                          You probably have a K19 Hynautic and H50 Helm. Should be a mark on the gold colored end. Spec says 8.3 cu in. Here is link to spec sheets

                          Adams, Marc Ô£å [email protected]


                          to me, Jason

                          Images are not displayed. Display images below - Always display images from [email protected]

                          Ken / Jason:

                          By the drawing that was provided. The feeder line from the bottom of the reservalve has been removed for some reason. (this is the line that comes off of the larger fitting on the bottom of the reservalve, it is to go to the a/p return line and the helms return line)

                          This may pose a problem with operation..

                          The K-19 is a "balanced" cylinder;

                          If the cylinder is actually marked K-19, then we know it is balanced as Hynautic, nor Teleflex has ever made an un-balanced cylinder tagged with a K-19 part number. Suggest that this cylinder part number is double checked and confirmed.

                          The cylinder shaft exits both sides of the cylinder body equally, however. One side the shaft is enclosed in a tube, so, you cannot see this side, but it is there.

                          It sounds to me like there may be a problem with the a/p pump. I say this as when the close out valves are in the "closed" position, the manual circuit works..



                          From: Ken Jennings [mailto:[email protected]]

                          Sent: Monday, September 27, 2010 6:46 AM

                          To: Bohl, Jason

                          Cc: Adams, Marc

                          Subject: Re: GHP 10 NMEA 2000 connection with Furuno NN3D


                          I have cc'd you as I need you to forward this to a technical support person at Teleflex. To solve this we will need someone who is an expert on Hynautic 3 line steering systems such as were installed on 1988 Bayliner 3818s


                          Thank you for the assistance & concise instructions.

                          Unfortunately I was not not able to complete all of the testing.

                          I ran into further problems with the Garmin pump & the Hynautic steering system.

                          A few months ago I read the FAQ (pasted in below) from Garmin's website & made the chances Garmin recommended to the hydraulic steering circuit. My diagram of the as installed circuit on my boat is attached. Garmin - Hynautic install diagra.pdf

                          ++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++++++++++++++++++++++++++++++++++++++

                          Question: Can I use the GHP 10 with my Hynautic Steering System? THIS WAS THE WRONG INFO ON GARMIN'S FAQ SITE


                          If the boat that is being equipped with the GHP 10 Autopilot has a Hynautic hydraulic system already installed, there are a few considerations to follow in order to allow the GHP 10 Autopilot to perform optimally.

                          The Hynautic system uses air to pressurize the hydraulic fluid in the steering lines. Hynautic recommends the system be at 25psi. Unfortunately this amount of pressure will cause issues with the GHP 10 components and may blow gaskets and seals. Garmin recommends using around 10psi for all of our components. We recommend setting the psi to 7 or 8 and at that point, turn the helm. If the helm moves normally, maintain that psi. If the helm does not move normally, the psi can be changed to correct the issue, however please do not increase the psi too much.

                          Also, the Hynautic system uses a reservoir which connects to the helm's return line. Since the GHP 10 pump needs to connect to the return line, disconnect the line that returns the fluid back to the helm and connect that to the return line on the GHP 10 pump.

                          Last modified on: 04/16/2010

                          ++++++++++++++++++++++++++++++++++++++++++++++++++ ++++++++++++++++++++++++++++++++++++++++++++++++++ ++++++++++++++++++++++++++++++

                          Despite the fact that the systems co existed since the end of July this summer, Sunday morning, I was faced with a non responding helms in the boat.

                          Sunday, each time (3 or 4 times) I bled the upper & lower helms according to instructions from Hynautic (Hynautic Purge with 3line.pdf) I was able to restore the boat's hydraulic / manual steering to both helms & control the rudders. However; as soon as I re introduced the Garmin pump back into the hydraulic circuit I was not able to control the rudders from the helms.

                          I did this about 3-4 times in various configurations, with the pump in the circuit & the pump out of the circuit, with the pump's shut off valves open & closed. I was successful in bleeding the system a couple of times. Each time I re connected the Garmin pump back into the circuit I lost my helms.

                          You can see the attached the bleeding instructions from Hynautic as well as a diagram of how I hooked the Garmin pump into the circuit after reading the Hynautic steering related FAQ on the Garmin site. I wonder how, using this Garmin recommended hydraulic circuit configuration with the return line connected between the reservalve & the pump, how is one supposed to be able to bleed the upper & lower helms? If the return line is connected to the Garmin pump, how does the oil (with a 40 psi head of air pressure from the reservalve) get fed from the reservalve up into the upper & lower helms during the bleeding process? This is unclear. I feel that Garmin & Hynautic need to do a little more work here on the circuit design and the attendant bleeding process. Do the pumps shut of valves need to be open or closed during this process? I would expect open but I still do not do not understand how the oil is supposed to get from the pump to the return line of the helms when the reservalve's return line is not connected to them at all.

                          By way of additional information on the subject; about 2-3 weeks ago I removed the unbalanced valve from the Garmin pump after being told by a Teleflex Hynautic tech associate that this was a balanced cylinder so for the past 2-3 weeks I have been running with the pump set up for a balanced steering cylinder. However; I am still suspicious that despite assurances from Teleflex Hynautic that I have a balanced steering cylinder model (K-19) that in fact; my steering cylinder is UNBALANCED. At hard over to starboard the cylinder rod is FULLY RETRACTED. At hard over to port the cylinder rod is FULLY EXTENDED. How can that be a balanced cylinder?

                          Images from

                          What I would like to do now.

                          I have removed the Garmin pump from the boat and would like to return it to Garmin for verification. In the meantime I will drive the boat manually as normal steering has been restored. Please send me an RMA form or number today so that I can send this pump back to Garmin for verification. I want to ship this pump from Buffalo NY tomorrow AM.

                          I would like verification from Hynautic that my K-19 steering cylinder is a balanced steering cylinder.

                          I would like to see Garmin & Hynautic co operate to jointly draw a Visio diagram of the recommended steering circuit complete with purging instructions with the pump in the circuit.

                          Many thanks as always.

                          Please call if you have any questions related to this email.


                          cell 416 570-4957