1990 Johnson Evinrude "ES" 40 thru 55, P/N 507872, Page 291Get this manual
DOWN 1When the DOWN button is pressed, the pump rotates in clockwise direction2Fluid pressure opens the DOWN check valve and moves the pump control piston which mechanically opens the UP check valve 3Fluid pressure is directed to the top of the cylinder to move the piston DOWN4Low pressure fluid leaves the bottom of the cylinder, moves through the open UP check valveand returns to the pump 5To allow for the volume differential caused by the piston rod, excess fluid is vented to the reservoir through the DOWN relief valve CD6When the piston is completely retracted, pump output is vented to the reservoir through the DOWN relief valve CD to protect the unit from extreme operating pressures7When the unit is operated in the DOWN direction or when the engine is running in REVERSE gear, the following components must hold pressure: Impact Relief valves Up relief valve Piston a-rings Down check valve Filter valve and seat Q) External leaks