I thought I had to replace my rudder bearing on my 1991 390 this past winter. I had about 1/4" play vertically in the rudder and about 3/8" play in it horizontially. I called the folks in Marion, SC (Ward Richardson REALLY KNOWS these boats) and they said I should only have about 0.5mm play or less in any direction. I thought, okay, bearings are bad. He was suspect that it would actually be the bearings. He said the upper bearing, which is really just a MPFE (teflon?) bearing rarely goes bad. Its 99% of the time the lower bearing or copper bearing sleeve. He sent me the replacement manual in PDF format of how to replace the bearings.
Took the rudder out (very easy to do) and found the play was in the fiberglass housing that the copper sleeve sits in. The fiberglass housing had worn down. It was only a minor wearing, but enough to cause the play I had. The veritical play was the teflon ring just below the lower bearing was worn.
So, I ordered a new lower teflon ring ($65 from Beneteau) and used 3M 5200 to build up the worn fiberglass and reset the copper sleeve in place. Came back a week later after the 5200 dried and reassembled the rudder. PERFECT fit. No play in the rudder vertical or horizontal.
I attached the rudder bearing instructions that I received from BeneteauUSA and the diagram from their site of my 390 rudder system.
Good luck!