A system for positioning a rotatable vessel includes a rotatable vessel having a target block fixed thereto. A protrusion that is configured to mate with the target block is coupled to a slide plate and moveable relative to the slide plate toward the target block. The slide plate is slidably adjustable relative to a fixed base plate. The precise rotational position of the vessel can be controlled by fixing the slide plate relative to the base plate, such that when the slide plate is locked to the base plate, extension of the protrusion into engagement with the target block will rotationally position the vessel. When the protrusion and the target block are engaged, the vessel and the slide plate are linked, and the position of the slide plate may be adjusted relative to the base plate to set an adjusted desired position of the vessel.