How to Maintain a Hydraulic Steering System

By Mike Smith

Maintain That Course!


Hydraulic Steering System

Hydraulic steering is a wonderful thing, especially for those of us who remember old-fashioned, jump-the-sheave cable systems or, even worse, the chain-and-sprocket setups popular on sailboats. While some folks (sailors, mostly) criticize hydraulics for the lack of “feel,” others say that’s one of the main benefits: You’re not constantly fighting the pressure of water rushing past the rudder. Even better, hydraulic steering is reliable and demands little maintenance—like a Timex, it takes a licking and keeps on ticking. But you can make the ticking smoother, and ensure against the odd system failure, by adding periodic steering-system checks to your maintenance schedule.


Folks who venture far offshore pile redundancy on top of redundancy, and most include a means of emergency steering along with mountains of spare parts and survival rations. But do you need emergency steering if you have a well-maintained hydraulic system? Maybe not. Here’s why.

Emergency steering sometimes consists of an emergency tiller, which most likely was last seen onboard at some point during the Clinton Administration. Most emergency steering arrangements are poorly designed and rarely tested: If you have one, try to set it up and use it but don’t be surprised if it’s useless. Serious bluewater cruisers engineer elaborate and expensive emergency systems for their own long-range yachts, but even they don’t always work very well.

And many steering failures result from hitting floating debris and damaging the rudder or rudders, in which case an emergency system, even a functional one, won’t help. You’ll need a back-up rudder or rudders, too, and not many boats are so equipped.

The bottom line? If you have hydraulic steering, and most serious cruising boats do nowadays, learn to maintain and repair it, and carry enough spare parts to rebuild it underway if necessary. Stow a spare helm, spare steering cylinder, plenty of spare hydraulic oil, and an assortment of spare hoses in your parts locker. Even better, replace the hydraulic hoses with durable, damage-resistant copper tubing. If you have multiple helms, add shut-off valves so you can isolate each of them, as well as the autopilot, in case of failure, and a bypass valve so if you do hit something hard, the impact will dump the pressure from the steering lines and let the rudder swing clear before it’s damaged. At least, if you’re lucky.

Let’s start off by facing facts. Hydraulic steering demands so little attention, most of us never open the owner’s manual—we just turn the wheel and the bow swings accordingly. So step one is to find the manual, or download one. The section on maintenance will tell you all you need to know. Once you’ve finished with your reading, it’s time to get physical.

If your steering has been behaving properly, just check the oil and do a visual system check; if your wheel has been feeling “bumpy,” there’s probably air in the lines, which means bleeding or “purging” them according to instructions in the manual. Dirt in the helm’s check valves can also cause that bumpy feeling; in the latter case you’ll have to clean the lines first, again according to instructions, then bleed and purge them.


There’s a bit more to checking the oil than you’d think. First, make sure it’s topped up to the level stated in the manual, which usually means leaving a little air space for expansion. If you have to add oil, follow the directions—different systems call for different procedures. Typically, you check and fill either at your highest helm station (in a “two-line” system) or at a remote reservoir tank (in a “three-line” system).

In a two-line system, by the way, the helm pumps oil through the hydraulic lines, helped by gravity in multi-helm boats: A compensating line between the helms lets oil flow down to the lower helm while trapped air rises and escapes through the vent fitting on the upper one. Three-line systems, on the other hand, fill at a separate reservoir that’s pressurized to push the hydraulic fluid through the system. They are usually found on larger boats, but my old Hatteras 34 from the early 1960s had one (which was still working faultlessly when I owned the boat, 20-some years after she was built), so maybe your classic boat does, too. Three-line systems are a little more complex, but they’re easier to check and top off.

On thing you should bear in mind when adding oil—you need to release the pressure in the reservoir first, and then pump it back up afterwards; SeaStar Solutions (, a major player in steering hydraulics, recommends 40 to 45 psi. And remember if your system appears to be topped off even if you haven’t checked it for a while, chances are all is copacetic, and you just have to do a visual check for minor leaks, chafe or kink points in the lines, broken oil-line support straps, etc.

Typically two stainless-steel, T-type fittings feed hydraulic fluid to the steering cylinder (in some cases via bushings like the two shown below) and, when bleeding air from the system is necessary, the bronze fittings (which are capped when not in use) facilitate.


Put your steering system under pressure to check it out, which is where a helper will come in handy: While you’re inspecting potential leak sites, have him/her hold the wheel hard over, first one way, then the other, hard enough to engage the pressure-release valve and make the helm chatter as the valve opens and closes. This will pump enough psi into the lines to make even micro leaks show up. (Cranked hard over the helm pump can generate up to 1,000 psi or more.) Wipe each connection with a paper towel; if you see any oil on it, investigate further. You may have a loose connection, or maybe a damaged hose fitting. Some steering systems are plumbed with damage-resistant copper tubing with repairable end fittings. Others use flexible hydraulic hoses with factory-attached end fittings; if one is leaking, you’ll have to replace the whole hose.

You may find valves in your steering system: First-class installations include one or more of an assortment of valves, each of which makes using, and maintaining, the steering easier and even safer. Valves add more connections and therefore more potential leak sites, but they are well worth the slight added risk. There are valves to isolate parts of the system and minimize oil loss if something has to be disconnected, for example, an autopilot: Without shutoffs, of course, removing an autopilot for repair would spill lots of oil. If your autopilot doesn’t have shutoffs, adding them would be a worthwhile investment.

Optional bleed valves close off the steering cylinder in hard-to-bleed, multiple-helm systems, letting the upper helm act as a pump to push oil into the lower ones as well as the compensating line. And an emergency bypass valve is often installed to open and release pressure should the rudder take a whack; otherwise the sudden surge of pressure from the wrong direction could blow out the check valves in the helm or burst an oil line.


Ensure gear stowed in your lazarette or steering compartment can’t fall onto the steering cylinder and damage the ram (the stainless steel rod attached to the tiller arm). A scratched or dinged ram will wreck the seals and let oil leak out. There’s no sense replacing seals if the ram is damaged, so repair means replacing the ram, which usually means replacing the whole cylinder. It’s easier, and cheaper, to protect it in the first place.

If the ram is okay but the seals are leaking, replace them. There can be one set or two sets per cylinder, depending on whether the cylinder is balanced or unbalanced. (A balanced cylinder exposes the ram on each end, although only one end is attached to the rudder; it has seals at each end. An unbalanced cylinder’s ram extends from one end only, and therefore has only one set of seals.) Replacing the seals involves disassembling the cylinder, so it’s best done in a clean shop by a qualified mechanic—a good reason for checking out your steering within easy reach of your boatyard, and not waiting until something breaks down far from home.


Now, before you leave that lazarette, give the rudder(s) a once-over, too. Check that the steering cylinder is securely connected to the tiller arm and that the tiller arm is securely connected to the rudderpost. In twin-rudder boats, check that each end of the tie bar is properly attached. Look for corrosion everywhere, and mold, too: This part of the boat is usually damp and rarely well ventilated. Inspect the stuffing boxes for your rudders as well—If they are of the conventional type they should show signs of a little water seeping in for lubrication. If too much water’s coming in, you should tighten the stuffing box, but not too much: Loose and leaky is better than overtight. If in doubt, ask your mechanic to check it out.

And finally, keep this theme in mind. Don’t look at your steering system with tunnel vision. While you’re inspecting it and perhaps working on it, look around for other issues, things like broken bonding wires (the green ones), loose or broken wire straps, signs of water leakage, corroded fittings and fastenings, and so forth. Make your steering-system maintenance adventure serve multiple purposes, and jot down in a notebook anything you see that needs attention. Visiting the innards of your boat regularly can head off not just steering problems, but others as well.