A joint connecting a cylinder actuator of a trim tab to a watercraft includes a first part couplable to a wall of the watercraft, a second part couplable to the cylinder actuator, a pin coupled to one part and a pin seat formed in the other part. In one embodiment, the seat is defined by a portion of a circular cylindrical surface having an opening on one side. The surface portion has an angular extension larger than 180°, and the pin has a correspondingly cylindrical portion with a laterally flattened surface for introduction into the opening of the pin seat. The opening of the cylindrical pin seat and the flattened portion/s of the pin are in such reciprocal angular positions that the two joint parts are operably connectable and disconnectable by disposing them in a relative angular position, which cannot be attained in the mounted operating condition.