The 7158 is a custom built full-power follow-up unit, designed to provide power steering to manual steering systems on larger vessels. The unit contains a 4-way closed centre solenoid valve. This valve accepts electric signals from jog levers, electric full power follow-up levers or auto-pilots.
Solenoid valves installed into a steering system must be of the soft shift type. If multiple solenoids are used, they must be of a closed centre type. It has maximum supply pressure of 2,000 PSI (138 bar). The maximum output flow is 60 GPM (227 l.).
The photo shown is of a 7148, very similar to a 7158.