Originally Posted by simon23
Does anyone know the spec of the fluid in hydraulic steering.don't know the make of the unit.are they all the same ? thanks
Sent from my GT-S5830 using Rib.net
It's a military grade aircraft hydraulic fluid. The spec it's supposed to meet is MIL-H5606 rev G (the rev suffix may be wrong.) Seastar's fluid is a natural color; most aviation grade stuff will be dyed for leak detection.
From the Seastar manual:
Recommended oils for your steering system are:
Seastar hydraulic fluid, part no. HA-5430 (1 quart), HA-5440 (1 gallon)
Shell Aero 4
Esso Univis N15
Chevron Aviation Fluid A
Mobil Aero HFA
Fluids meeting MIL H5606 specifications
Automatic transmission fluid Dextron II may be used in an emergency
In cases of extreme emergency, any non-toxic, non-flammable fluid may provide temporary steering.
Pretty much any hydraulic fluid will work fine; the seastar stuff is a fairly light oil to guarantee ease of handling. Heavier oils may make the steering a little heavier (though probably not much.)
I bought a gallon of Shell aviation hydraulic fluid for about the same price as a quart of Seastar fluid. A complete fluid replacement on my boat used maybe a third of the gallon.