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
• 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
• 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
• 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
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
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
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
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
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
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.
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.
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
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
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.
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
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.
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
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.
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.
steering trouble shooting and repair
Check hoses for cracks
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