Trim-tilt device for marine propulsion unit

A trim-tilt device for a marine propulsion unit, wherein a cylinder device is adapted to be mounted between a hull and the marine propulsion unit freely tiltably supported by the hull;

• and wherein a hydraulic fluid is supplied from a hydraulic fluid supply/discharge device into the cylinder device and is discharged from the cylinder device into the hydraulic fluid supply/discharge device to thereby expand and contract the cylinder device and thereby trim and tilt the marine propulsion unit,
• the cylinder device comprising:
• a housing connected to one of the hull and marine propulsion unit to form a large-diameter trim chamber;
• a cylinder telescopically inserted into the trim chamber and forming a small-diameter tilt chamber;
• a large-diameter trim piston fixed to an end portion of the cylinder within the trim chamber of the housing and serving to partition the trim chamber into a first trim chamber of a cylinder accommodation side and a second trim chamber of an anti cylinder accommodation side;
• a piston rod being connected to the other of the hull and the marine propulsion unit that is telescopically inserted into the tilt chamber of the cylinder;
• and
• a small-diameter tilt piston being fixed to an end portion of the piston rod within the tilt chamber of the cylinder and serving to partition the tilt chamber into a first tilt chamber of a piston rod accommodation side and a second tilt chamber of an anti piston rod accommodation side,
• a portion of the cylinder of the cylinder device which projects from the housing outward in a region of a trimming operation being covered with a tank constituting the hydraulic fluid supply/discharge device, and the portion of the cylinder which projects from the housing outward, being disposed in a hydraulic fluid of the tank.