1988 Johnson/Evinrude "CC" 40 thru 55 Models Service Manual, Page 309Get this manual
1To install gauges remove the manual release valveTo remove the valve: abUsing the trim switch, run the unit down completelyLoosen the manual release valve one full turn cMomentarily jog the trim switch "up," then "down," then "up"Failure to follow step below could result in eye injury to you or bystanderdSome residual pressure may be present in the hydraulic system when the manual release valve is removedRemove the manual release valve watching for residual pressure tending to push valve out