The plane flies straight and true. However, the rudder trim is counter clockwise as far as it will go. Physically stops, no more turn to the left. If you crank it clockwise the plane starts to yaw to the right. Plane is in annual now and I asked the AP to look into it. He just called and said everything is rigged to spec and he has taken apart the rudder trim mechanism and re-installed by the book. Same results. He is theorizing the wrong trim got put in as the 181, 161, and 141 all have different part numbers. The mechanism has zero markings so it is a theory. He said the correct part number is 65837-02. Throwing this out to the board to see if anyone has any other theories or have seen this in the past.