1978 Johnson 175, 200, 235 HP Outboard Service Manual, Page 176Get this manual
COMPONENT DESCRIPTION (See color schematics or Figures 9-3, 9-4, or 9-5 Trim Up Relief Valve This valve controls maximum oil pressure in the system during trim and tilt upIt also bleeds oil to the reservoir when the engine is run at speeds over 1500 rpm (approximately) in the partial tilt positionThis allows the engine to return to the maximum trim up positionManual Release This device allows manual tilting movement of the engineWhen this screw is loosened, the engine will not move in the trim rangeTilt Cylinder This hydraulic cylinder moves the engine through the tilt range onlyIt also absorbs the shock of hitting an underwater obj ectImpact Letdown Valve This valve is only used when the engine hits an underwater object and is forced to tilt up to pass the objectWhen activated, it provides an oil passage to the reservoir from the underside of the tilt pistonTilt Check Valve (inside tilt piston) This valve provides one way oil passage from the oil pump to the underside of the tilt piston while trimming and tilting upImpact Sensor Valve This valve is only in operation when the engine tilts up from hitting an underwater obstructionIt allows oil from the top side of the tilt piston to flow to the letdown control piston, which then moves to open the impact letdown valveFilter Valve This valve filters and allows make-up oil to flow from the reservOir to the system during automatic letdown after tilt up from underwater impactThe valve must close during down operation of oil pumpTrim Check Valve