Gone Outdoors

How to Change the Hydraulic Fluid in a Boat's Steering

by Will Charpentier

Most boaters with hydraulic steering don't realize that, just like your car's motor oil, your hydraulic oil must be changed periodically. The hydraulic oil change doesn't drain all the hydraulic oil at one time; that allows air to become trapped in the hydraulic system to cause nine kinds of havoc. Instead, the hydraulic oil is changed every six months, in June, and December.

1. Unscrew the filler nut on the helm, behind the steering wheel. Screw the end of the filler tube into the filler hole from which you removed the filler nut. Fill the helm with oil; when you see oil in the filler tube, the helm is full. Remove the cap from the hydraulic oil bottle, invert the bottle and screw the threaded nozzle in the oil filler cap. Use a marlin spike or nail to make a small hole in the bottom of the bottle.

2. Put an oil drain pan under the left cylinder bleed screw. Turn the wheel to the right until the cylinder rod on the left side of the piston is extended fully. Have a friend unscrew the cylinder bleeder on the left side.

3. Ask your friend to grip the extended cylinder rod and hold it, keeping the cylinder rod from going back in. Turn the wheel hard over to the right; as you do, a stream of oil will gush from the bleeder valve on the cylinder.

4. Tell your assistant to release the cylinder rod after about 1/2 bottle of oil has bled from the cylinder, and to close the left bleeder screw. Throughout this process, as the old oil is bled from the cylinder, new oil is sucked into the system at the helm. Keep turning the wheel to the right and tell your friend to move the oil pan underneath the right bleeder screw and to open it.

5. Tell your friend to grab and hold the right cylinder rod while you turn the wheel to the left. When a steady stream of hydraulic oil comes out of the right cylinder bleeder screw, tell your friend to close the right bleeder screw and relax: the oil has been drained and replenished.

Items you will need
  • Threaded oil filler (looks like a hypodermic needle with threaded ends)
  • Hydraulic oil
  • Assistant

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