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Yacht Charter Guide

Hydraulic steering

By: Scott Fratcher - Marine Engineer/Captain


In this article we’ll discuss how to maintain and trouble shoot and bleed hydraulic steering systems.


Hydraulic steering is the simple solution when a vessel desires-

• Multiple helm stations
• Simple autopilot installation
• A smaller steering wheel to gain more interior space
• The ability to easily control larger (over 100 hp) outboard motors
• Control multiple outboard motors stacked on the transom without the use of a connecting bar
• Dual rudders


Hydraulic disadvantages-leaks and creep

Leaks- Drips of oil in the bilge, and random messes are often considered part of living with hydraulics. Not so, says Doug Stewart of Hyspecs. “If you have to ad more than a teaspoon of oil there is a leak that should be found.”

Luckily in today's world of high tech modern fittings and specialty hoses this issue has been reduced considerably.

Tips to prevent leaks-
• Secure all hoses away from chafe points. Hydraulic hose moves slightly with a change of pressure (turning the helm) and each movement can mean chafe eventually leading to a leak.
• Use a small strip of 3M oil sorbent mat wire-tied around each fitting. This gives the operator an early indication if any leaks have formed and absorbs a drip before reaches the bilge.
• Lay a 3M oil sorbent mat under each cylinder so we can clearly see if a leak has begun. Even the smallest drop should be noted and traced out.
• Wrap all externally exposed hydraulic fittings with greased tape. Greased tape, purchased at any hydraulic shop, will prevent rust from starting.
• Don’t lean on the wheel. The wheel is actually hanging on the center shaft of the helm pump. If weight is put upon the wheel while turning, the shaft will eventually wear causing a leak.
• Use one brand of hose and connections on all fittings to prevent small inconsistencies in mating faces.

Amazing-The industry is full of stories of disasters that started with the use of the wrong hose. The most famous might be a launch that struck the Westport jetty after a steering failure caused by the use of garden hose in the hydraulic system.

Creep- If we turn the wheel left and right a few times the king spoke slowly changes position. This is hydraulic an example of “creep” and can make docking a challenge as the helmsman does not know exactly where the rudders are pointed. The simple solution is to install a rudder angle indicator.

Tip-Check your autopilot for a rudder angle indicator readout.

Note-Hydraulic creep will not account for a situation where a boat has weather helm and the rudder slowly “falls” away from the pressure. This is a bad cylinder seal, or an anti kickback valve. This is important and a sign that a larger failure is looming, possibly when the vessel loads the hydraulic system in large seas.


Air in a hydraulic system is the number one cause of inconsistent helm reactions. An autopilot or helmsman simply will not steer a straight course if there is air in the lines. Removing the air is not as simple as it might sound. In theory the air will rise to the highest level of the system and bubble out, but what if we have loop in a steering line or other air trap?

During installation the technician should aim for a gently sloping hydraulic line path to the helm pump, but this is not always possible. Frequently the system is left with loops, valleys, and points where air can collect. Lets look at ways to clear persistent trapped air.


Bleeding without a manual

Frequently a boat steering system will not have an instruction manual. This is because the steering system itself has been built from various components meaning we have to bleed the air through common sense.

This first step in bleeding air, says Doug Stewart of Hyspecs is deciding weather the project is within the scope of the DIY. Observe the steering cylinder. If it has a small cylinder stacked over the larger steering cylinder then this is a ‘follow up’ steering system and it’s best to call a professional. Also check if a hydraulic steering pump is mounted off the engine. If so seek a reputable technician.

The procedure listed below should work for most boats that have multiple of helm pumps and an electric autopilot.

Caution-Turn off autopilot when bleeding oil. An autopilot pump can build high pressure inside the steering tubes that can spray out during bleeding.

Locate the highest point of the system and top off the oil. The highest point will either be a helm pump or a reservoir tank. If the upper most helm pump has a tube in place of the fill plug then the system has a reservoir tank. Be sure this tank is full.

Turn the helm hard over and hold light pressure on the wheel. Have a second crew ready at the steering cylinder. The second crew should locate the air bleed screws on the cylinder and note the side of the cylinder under light pressure (extended side). Gently release the air bleed screw. Let a small amount of oil flow into a cup while watching for air bubbles. If bubbles are found continue bleeding till the oil is clear. The crew at the helm pump should continue to rotate and hold the light pressure on the wheel to keep the oil flowing from the bleed screw. Close the bleed screw, turn the helm the opposite direction and repeat. This should clear the trapped air inside the cylinder.

With the air clear from the cylinder we can now concentrate on removing the bubbles in the hydraulic connection tubes. This can be tricky. If the tubes were not installed with a gentle upward slope and happen to have caught air, turning the helm port to starboard may not produce enough oil flow to force the bubble free.

Technicians use a special pump that circulates oil through the lines at high speed to move trapped bubbles. A DIY method of pushing trapped air through the system is to manually run the autopilot in one direction while turning the wheel the opposite direction. This will produce a circular flow of hydraulic fluid through the hoses that can push the bubble along. Reverse directions and repeat the process.

If the hydraulic system has a bypass valve for emergency steering open the valve and turn the wheel quickly for three to four minutes to push the bubbles along. Reverse direction while keeping an eye on the reservoir tank for bubbles appearing. This is a sign your on the right track.

Alternatively the lower helm can be turned one direction while simultaneously turning the upper helm the opposite direction. This will produce a circular flow of oil that can push the bubbles out of the “sags” in the hydraulic hoses.

Bleed the air from the lowest helm pump. All helm pumps should be completely full of oil, but often they contain a small amount of trapped air.

Releasing the air can be tricky if the helm pump does not have vent hose. If the helm pump reservoir cap is opened oil will flow out of the fill hole due to the oil level in the upper reservoir tank.

For this reason we only slacken the fill cap while watching the area around the fill cap threads for bubbles or a swelling of oil. Wiggle (but don’t remove) the cap till all the air is released and oil begins to show. Close the cap and continue on to the next highest helm pump working toward the top pump in the system. Check the oil again leaving a small air gap for oil expansion.

Top off the oil and the steering system can now be tested and any improvements noted.

Tip-Many outboard steering system come with pre-made matched hoses, but they attach to opposite sides of the cylinder, thus a small amount of extra hose length will “bulge” at the helm pump. The bulge must be looped down or an air pocket can form causing “spongy” steering.

Tip- Stuart Hay of Lusty and Blundell recommends purchasing a complete steering system from one builder. This way if a problem surfaces you only have to deal with a single supplier.


Oil types

One of the main causes of hydraulic steering failures is use of the wrong oil. Check your manual and clearly label the helm pump and spare oil bottle left on the boat.

The recommended oil for most pleasure craft boat steering systems ISO 15 (check your manual), and up to ISO 32 for commercially rated systems. This is synthetic oil and should not be mixed with ATF power steering fluid, or break fluid.

Max Hall of So’Pac Maritime Limited states “Using ATF or other ‘wrong’ oil can ruin the seals and is a reason manufactures will void a warranty.”

Mixing oils can have greater effects than simply voiding a warranty. Oils contain additives that react with other additives forming sludge that can cause sticking in the anti-kickback valves resulting in complete system failure.

Often we hear the DIY say as the system wears you can use thicker oil to overcome hydraulic creep (see creep in this article). Stuart Hay of Lusty and Blundell warns this is not the correct solution as thicker oil makes for heavier steering while light oil makes for easier steering. The steering system was designed for one oil, and that is the oil to use.


Steering Cylinder

The cylinder is the workhorse of the system. It takes very little maintenance during its life, except the mounting and end points will often need a small amount of grease.

The cylinder should be balanced. In other words, it must produce the same movement in each direction for the same oil pumped. This is different than a cylinder typically seen on heavy equipment.

Steering cylinder installation
Hydraulic steering can cause increased loads on mounting hardware compared to traditional steering systems. This means we must increase the strength of the rudder quadrant, tiller arm, and the cylinder mounting point to the hull compared to traditional steering systems.

This increased load is because a hydraulic steering system “locks” the cylinder when inactive. This means if a large wave or grounding were to occur the cylinder will hold the rudder in position until something breaks. This is different than a chain to cable steering system that will simply back spin the wheel. It is this extreme force that must be planed for when installing a hydraulic steering cylinder.

The push/pull effect of a cylinder can be a difficult load to contain. Simple securing bolts often are not sufficient to prevent “wiggle” at the mount resulting in loose bolts and noisy steering. The solution is to “box” in the mounting point. This can be an epoxy lip the cylinder butts against, a steel strip welded down, or other method of securely holding the base plate of the cylinder from sliding.

Common challenges in hydraulic steering systems


Alignment of rudders

Twin engine, or twin rudder boats, such as catamarans often use a pair of balanced rams. This can lead to complications like out of align rudders or motors.

To re-align the rudders turn the helm hard over till the rudder hits the stops. Keep turning the wheel and verify both rudders are against the stops. Repeat in the opposite direction and the rudders will be correctly aligned. Repeat this procedure as often as necessary.


Cylinder pumps too small

Doug Stewart of Hyspecs tells us “A typical steering system should be able to turn lock to lock in five seconds, or one wheel turn per second.”

Occasionally a steering system is installed that needs seven or eight turns lock to lock. A cylinder too large or a helm pump too small causes this miss-match. The only solution is a re-design, so the components match the intended use.


Insufficient power

The cylinder should have the power to put the helm hard over at full speed. This can become a problem when an undersized system is installed. Max Hall of So’Pac Marine Limited states “The helm must be able to turn 35 degrees at full boat speed without stalling the rudder.”

Note-It’s important to watch the cylinder itself during this high speed test as it’s difficult to know if the helm simply stalled during operation only to recover after the vessel slowed.

Steering hoses kinks
From the helm a kink will feel like the wheel is difficult to turn in one direction while easy in the opposite direction. This used to be a larger problem till a few years ago when specialty re-enforced hoses were brought onto the market. These new hoses can now make a tight turn and not collapse. The permanent fix for kinked lines is to replace them with a modern style.


Helm slipping

The feel of a helm pump (wheel) should be smooth and quite in both directions. Occasionally a helm pump will make a “thunk, thunk” sound during turning.
This can be caused by-
• Air in the system
• Excessive play in the helm pistons
• Broken springs in the helm pump

The air can be bled, but the wear in the pistons or broken springs are difficult to repair and most manufactures recommend simply exchanging the helm pump with a new one.



Hydraulic steering has the advantage of straightforward auto pilot installation. This is because the existing steering cylinder can also serve as the auto pilot cylinder, so the pump is simply Tee’ed into the steering lines. This saves money as no second steering quadrant and connection to the rudder stock is needed. Of course this also means no secondary backup has been installed on the steering system.

It should be noted an autopilot pump working hard can heat the oil. Hot oil expands up to ten percent meaning extra space must be left in the header tank or top most helm pump to allow for this expansion.


Spare parts kit

During the installation of the steering system it’s a good idea to purchase a couple extra re-usable fittings and a small selection of hose along with a few liters of the recommended oil. Label and wrap the parts then store onboard in a safe place. In case the eventual steering failure were to occur you have everything onboard to make the proper repairs.


Galvanic corrosion

Hydraulic connections must all be made of the same metal. Steel fittings connected to stainless fittings are a common error that will soon rust (galvanasize) causing a leak, and possible rust intrusion into the hydraulic system.


Future of hydraulic boat controls

Hydraulic systems are easily interfaced with remote pumps and electronic valves. This means remote steering, currently controlled from a simple wireless handheld box, will graduate to more integrated systems such as the new Volvo IPS-Inboard Performance System.

The Volvo IPS controls docking speed and steering with a single joystick. Other manufactures are working on similar systems that will simplify boat control in tight quarters.

The day is coming when we can expect to see boats maneuvering at the dock with the driver pacing the stern deck, operating the engine controls, and handling dock lines all while talking on the cell phone.


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Volvo IPS drive

Hydraulic drive system

Hydraulic rams in use

Broken steering chain

Steering chain being repaired

Close up of broken steering chain

Leaking steering ram with oil sorbs mat

Leaking steering ram

Steering ram with pump installed

Earthrace bleeding steering system

Earthrace fixing steering

Pete Bethune making repairs

Author fixing Earthrace

Electric steering system

Hydraulic pumps off main engine

System shifting valves

Catching a steering ram drip

Big steering leak

Method of locating hydraulic drips

Steering pumps

Volvo IPS from below

Manual steering system

Hydraulic steering ram in good condition

Auto pilot head

Wind vane

Broken linier drive base

Reserve steering system

Steering system in operation

Emergency repairs of steering drive


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