Hynautic hydraulic steering.

The pressure on each side of the actuator is the same when at rest. The force used to move the control provides the differential pressure that moves the actuator. It is a simple pair of double acting hydraulic cylinders where the fluid leaving the "tank" side of an actuator cylinder goes back to the tank (reservoir) that refills the opposite side of the control cylinder. When the movement of the control is reversed, the flow reverses. In one direction a cylinder port is pressure and the other is tank, in the other direction those labels are reversed.

If the tank did not exist and no fluid reservoir was provided the system would work just as well until air leakage into the return side made it too spongy to be reliable. The air pressure on top of the hydraulic fluid (water/glycol in this case) is to provide a substantial buffer against air leaking into the system ... there is no way it can possibly boost or "assist" the movement of an actuator. This is hydraulics at its most fundamental level.

Disassembly of an actuator would reveal a double pilot check valve. I have had the check valve seize up, possibly due to the use of the wrong fluid. I also found severe corrosion in the reservoir. 50/50 glycol and distilled water is the prescribed fluid.

I buy the fluid from Hynautic and it comes in a gallon jug already pre-mixed, you just pour it in. It seems to solve these corrossion issues as I haven't seen them and for as little as you use 1-2 gallons in most systems it's well worth it. The biggest issue I've seen is the filter screen at the resevoir gets plugged up with debris making shifting and throttling take A LOT more effort and needs to be cleaned if you disassemble the system. I've also seen the resevoir fail at the lid crimp a few times and allow the air to leak out. But, needless to say this is a thread about steering that somehow got derailed with hynautic engine controls. 5

Not really, post #16 referred to the engine actuators and was followed by some erroneous thoughts about how the system works and why the engine actuators use higher pressure.

This is a forum for sharing information. Correcting false information and busting myths about the topic under discussion is hardly "derailing" a thread.

Correcting erroneous posts, yes I agree. But, the thread was about an Origional posters post was about hynautic STEERING on his cabo and how that worked. Somehow the thread got into hynautic controls at post 15 which isn't what the thread was about to begin with or what the OP was asking, however all of his questions were answered long before that.