Trailer or lift with boat centering provisions

The invention relates to boat trailers and boat lifts and, more particularly, to centering provisions for assisting guidance and centering of the boat when being re-loaded onto the trailer or parked in a boat slip. The centering provisions include laterally opposed centering constrictors that transition from an OPEN state defining a passageway width allowing free passage of the boat during launching and loading operations, and, a CONSTRICTION state defining a constricted width that is narrower than the passageway width such that the centering constrictors provide guidance and centering of the boat when being loaded onto the trailer parked onto the lift by contact along the boat's rub rail, gunwale or sides at elevations lower than the top ends of the constrictors or their mounts.