Adding fluid to Hynautic steering (48YF)

[Jammin']

We are getting ready to transport our boat home and my mechanic tells me I must have a hand pump on board to repressurize the Hynautic steering, if necessary, to 20 - 25 lbs.

[rsmith]

The reason the system is pressurized is to keep air out of the system not to force fluid anywhere. If you think about it the system is all at a static uniform pressure. This keeps the seals under pressure and sealed. If there is any minor leaks it’s leaking out and not letting air in. Once air gets in the system even the slightest bit the helms get air bound and cavitate.

[racclarkson@gmail.com]

The reason the system is pressurized is to keep air out of the system not to force fluid anywhere. If you think about it the system is all at a static uniform pressure. This keeps the seals under pressure and sealed. If there is any minor leaks it’s leaking out and not letting air in. Once air gets in the system even the slightest bit the helms get air bound and cavitate.

And how is this air kept out of the system? It is displaced by fluid from the reservoir that just accumulates there until the added air pressure pushes it into system to displace the air. And, minor leaks do allow air in when reservoir pressure is low allowing fluid to accumulate there.

[31FlyCruzr]

If it ain't broke don't fix it!

Do you have a leak, are you loosing pressure? I would pump up to 25 psi and keep going if it is working properly.
Half a reservoir is plenty of fluid.

Pressure is needed to push the fluid up to the helm pumps, it is static head for the three line system to keep air out.

Bill

[rsmith]

And how is this air kept out of the system? It is displaced by fluid from the reservoir that just accumulates there until the added air pressure pushes it into system to displace the air. And, minor leaks do allow air in when reservoir pressure is low allowing fluid to accumulate there.

Nooooo the reservoir just maintains pressure on the system. Air can not enter the system as long as there is any pressure. Fluid leaks out until the pressure in the reservoir is 0. Extra pressure in the reservoir doesn’t do squat as long as their are no leaks. RTFM

[racclarkson@gmail.com]

Well I have the manual, useful. Regardless of theory, air can find its way into a system that shows no visible leakage when the reservoir air pressure is low. It’s helpful in such situations that Seastar has good technical support. They point out making a system air tight can be more challenging than making it fluid tight. They specifically note that difficulty in very old systems, when not in use and with insufficient air pressure, where fluid tends to drain back to reservoir creating a void. “Nature abhors a vacuum.” Hence, keep the pressure up to force fluid into the system to prevent voids. Their advice.

[davidwigler]

The fluid is about half full and the pressure was at 15 psi.

Half full is fine. There should be a fill line below half full. What is the problem?

Don’t fill it. It needs air to pressurize the system.

[Pascal]

Air should not enter the system unless there is a leak as hydraulic steering is designed to be sealed. Many smaller boats (single helm) don’t have a reservoir and are simply filled by gravity at the helm pump. Works fine for years without air coming in.

[Dan Mapes]

We lost steering in the Bahamas while docking. All along the years we had the boat the gauge indicated 25psi. As it turned out the gauge froze and air got into the helm because there was no pressure. I will suggest an occasional test that cycles the air gauge.

[rsmith]

Well I have the manual, useful. Regardless of theory, air can find its way into a system that shows no visible leakage when the reservoir air pressure is low. It’s helpful in such situations that Seastar has good technical support. They point out making a system air tight can be more challenging than making it fluid tight. They specifically note that difficulty in very old systems, when not in use and with insufficient air pressure, where fluid tends to drain back to reservoir creating a void. “Nature abhors a vacuum.” Hence, keep the pressure up to force fluid into the system to prevent voids. Their advice.

Mr Clarkson we’re talking Hynautic not Seastar Sea star is a completely different system that is unpressurized. The reservoir is in the steering head where any air in the system is supposed to collect.