1978 Johnson 175, 200, 235 HP Outboard Service Manual, Page 173Get this manual
TILTING OR SHALLOW WATER DRIVE (See Figure 9- 3) While running in the shallow water drive mode or while the motor is tilted, the following valves and seals are pressurized and must holdaThe shock absorber valves in the tilt piston eThe trim check valvefThe tilt check valve
gThe trim up relief valvehThe impact letdown valveiAt approximately 1500 psi the trim up relief valve will open allowing the oil to return to the reservoir and the filter valve will open replacing oil to the top of the tilt cylinderThis occurs between 900-1500 rpmThe tilt cylinder will retract, lowering the motor to the fully extended trim pinsRetraction of the trim pistons, under thrust is prevented by the tilttrim separation valve and the trim check valve