Tips on hydraulic steering system maintenance

Hydraulic steering is often overlooked during maintenance operations.

In its most basic form, the hydraulic steering is made up of three components: a pump with an integrated hydraulic oil tank, a cylinder that connects to the engine (or rudder) and connection pipes that send the oil to the cylinder, which pushes the outboard motor or rudder in the desired direction.


The hydraulic steering should be checked at least once a year. With proper care, a hydraulic steering system will last a very long time. Flush your steering with your engine, using a jet of water (no high pressure), then wipe the steering with a clean cloth.

Look at the seals on the cylinder. The stem should never be oily. If so, wipe it with a cloth and check it again during an entire edge-to-edge steering cycle. If oil comes out of the cylinder, it will need to be replaced. Also check for pitting on the shaft, a sign of corrosion that will cause hydraulic fluid to leak from the cylinder.

Remove the vented cap from the hydraulic tank at the helm and take a sample of hydraulic oil. Is the oil black? Does it have a strong odor? The hydraulic steering fluid is transparent, mainly odorless and slightly colored. It is specially formulated with viscosity stabilizers, anti-wear and anti-foaming agents and corrosion inhibitors. It is the best oil to use in hydraulic steering systems. (Any oil conforming to MIL 5606 can be used.)

If the hydraulic steering oil sample contains impurities or is contaminated, the entire system must be drained and the hydraulic oil replaced.
Abrasive dirt is the biggest killer of hydraulic systems and often comes from debris during the initial installation of the steering system. Dirt or dust can enter the system when the pipes are cut and the fittings are installed. It is always best to make sure the pipes are clean before hydraulic oil enters.

It is recommended to drain the system and replace the oil every five years, making sure to bleed the system to remove air bubbles.

Go to the command line. Is there oil visible around the seals behind the steering wheel? Is the bar spongy when turned? There may be air in the system that needs to be emptied. If the system has already been purged and all the air has been removed from the lines, this may indicate that there is a leak somewhere. A sponge bar can also indicate that the piston or steering pump is leaking inside, which you cannot easily see. If you had to do three and a half laps so far and now do five laps, you’ve got a leak somewhere.
The oil does not evaporate and is not consumed by the use of the steering. So if you have to add oil to the tank, you have a leak.

Check the hoses and connections between the rod and the cylinder with a clean cloth at least once a year. Is there humidity in the connections? Plastic pipes that sneak into the back of the steering cylinder can become brittle and crack over time, although they are generally protected from the weather for this reason. These are the most exposed rubber hoses, but they are also easier to inspect.

On larger boats, this annual inspection takes longer, but the process is the same.