This document describes my method of rebuilding a steering ram. The boat is a Catana 471 and actually has two rams. If you have ever rebuilt a car master cylinder, you will find this to be an easy task.
Remove the Cylinders
Open the bypass valve to allow you to adjust the cylinder position to conveniently remove the bolt through the steering Quadrant.
Close the shutoff valves to allow you to drain just the cylinder, while keeping fluid in the rest of the system.
Bleed the cylinders into a pan, by pushing the ram in and out several times. Note that the socket used to hold the tubing ends in the pan. This will keep the tubing in the pan and mess at a minimum.
Disconnect the ram hydraulic connections and finally remove the ball joint cover at the other end of the ram cylinder.
Replace the Seals
You will not be able to remove the end cap without removing the ball joint. Before removing the ball joint, it’s a good idea to take a measurement so that you can create the same pushrod length when you reassemble the RAM.
Remove the four nuts and washers at one end of the ram. Pull the end cap off. Push a clean rag through the cylinder. The walls should be shiny and smooth.
Remove and replace the o-rings and seals being careful not to damage the adjacent machining. On the ram rod is the Bypass seal. This seal has two parts, a flat tough ring that is much less stretchy than a typical O-ring. Underneath that is a standard O-ring that lies in the same groove. I was able to stretch the new seal into position with a little hydraulic oil for lubrication, but without the use of tools. A tool might damage the sealing surface.
Note that the shaft seals in each endcap are installed with the concave surface facing in towards the cylinder.
Reassemble the Cylinders
The key here is to keep it clean. Lubricate all the rubber bits with fresh hydraulic oil and gently reassemble the ram into the cylinder. You may have to compress the bypass seal to get it into the cylinder without jamming it into the edge of the cylinder. Finally, replace the endcaps. Before tightening the nuts, be certain that the cylinder is rotated such that you can read its label when the ram is installed.
Reinstall the pushrod ball joint at the appropriate length.
Bleed the System
Close the bypass valve and open one of the disconnect valves and its bleed screw. Turn the wheel in the appropriate direction until no bubbles are seen coming from the bleed screw. Close the bleed screw and repeat for the other half of the ram. I repeated this a couple of times to be sure. While bleeding it’s a good idea to have another person keep an eye on the fluid reservoir to be certain that you do not introduce new air to the system by letting the reservoir run dry.
Be certain that your cylinder operates properly from stop to stop, and for catamarans that your rudders are synchronized per manufacturer’s specification.
The seal kits are available through PYI in the United States. The kits are pretty expensive If memory serves $109 each. If you were dissecting your system in a large city, I might find a shop that repairs forklifts and see if they can match up the seals.
My kits included an additional pair of seals that are replacements for a different vintage of Ram.
Finally, of course this document is meant to help you decide if this project is within your abilities. If you are in doubt, you should seek professional assistance.