Hydraulic assist device for marine propulsion unit

The hydraulic device for interpositioning between an outboard propulsion device and a watercraft transom for controlling the trim position of said propulsion device relative to said transom, said hydraulic device comprising a cylinder assembly adapted to be affixed to one of said transom and said propulsion device and defining a fluid cavity, a piston reciprocally supported in said fluid cavity and dividing said cavity into first and second fluid chambers, means for operatively connecting said piston to the other of said transom and said propulsion device for effecting a relative movement of said piston and said cylinder upon movement of said propulsion device relative to said transom, a first passage containing an absorber valve for permitting flow from a first of said chambers to the second of said chambers when a predetermined force is applied, a second passage comprising a let-down valve for permitting flow from said second fluid chamber to said first fluid chamber when the force is removed, a bypass passage containing a release valve for selectively communicating said chambers with each other and for normally precluding flow between said chambers but permitting flow between said chambers for effecting manual tilt-up operation, and a floating piston contained within one of said chambers for fixing the trim adjusted position of said propulsion device, said release valve comprising a housing defining a flow passage extending therethrough, a ball-type valve contained within said housing and urged by a coil compression spring in an axial direction to a closed position, and means for moving said ball-type valve transversely relative to said flow passage from its closed position to the opened position.