Hynautic, Inc hydraulic engine controls

[timtrose]

Looking for input. I have Hynautic dual station (upper and lower) twin engine controls. I can no longer get the starboard (slave) throttle to go above about 5% from the lower helm. Feels like it is binding up. I can go to the upper helm and the throttle easily goes through full motion and at the same time the lower lever follows full full motion as it should. Any suggestions as to where the issue is that is preventing the lower lever from moving? Check valve? Anyone know of a Hynautic engine controls tech in the Anacortes, Seattle area? 

[Greg Hansen]

Can you monitor the hydraulic pressure at the engines?  You probably have to add a gauge, which would be a real pain.  Then monitor the pressure with inputs from either station.  You would probably introduce air in the system, which would have to be bled out.

I would suspect something is restricting the flow/pressure of the hydraulic fluid.

I had a similar problem with electronic controls with multiple stations.  I was able to monitor the voltage of a 0 to 10 volt signal, with 5 volts being neutral.  6 to 10 volts was forward with increasing engine speed, 4 to 0 volts was reverse with increasing engine speed.  I had a loose wire, which dropped the voltage to 0, and caused the engine to go full reverse.  It was quite exciting with a 502 cu in Mercruiser V8.

On Wed, Jul 9, 2025 at 10:47 AM timtrose <timt...@gmail.com> wrote:

Looking for input. I have Hynautic dual station (upper and lower) twin engine controls. I can no longer get the starboard (slave) throttle to go above about 5% from the lower helm. Feels like it is binding up. I can go to the upper helm and the throttle easily goes through full motion and at the same time the lower lever follows full full motion as it should. Any suggestions as to where the issue is that is preventing the lower lever from moving? Check valve? Anyone know of a Hynautic engine controls tech in the Anacortes, Seattle area? 

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[timtrose]

I resolved the issue by moving the FB throttle forward, then going to the lower helm I was able to move the throttle lever full forward and back. I did not determine the source of the problem, but it is currently operational. I may consider flushing the system, filling with new hydraulic fluid and bleeding the system. Not today though! 

[Greg Hansen]

I think you're on the right track. Some sort of contamination in this system, especially if it's been a long time since it's been flushed. 

Does it have an accumulator that you pressurized, with air or nitrogen, to keep this system pressurized? If that system lost pressure, or had some sort of contamination in it, it could have caused restriction at one of your control stations.

You may have succeeded in flushing the restriction out of that control station.

Doing a good flush of that system will give you the best chance of avoiding future problems.

I worked on control systems for over thirty years and figuring out what you have to do to maintain and keep them operational is always a challenge. And I don't have any specific experience on boat hydraulic systems. Just try to use common sense and figure out the best and easiest way to resolve the problem.

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