Problem is that after 20 years the balls are gone, eaten by the sun and the sheaves don’t spin very well. But to replace is quite easy, takes a few minutes only. The most difficult part is to remove the sheave.
I have tried 2 approaches:
1. Using a hydraulic press, pressing out the center tube and parting the steel side from the tube. This works but was unnecessary work.
2. Just prying up the disc with a screw driver, be gentle.
The balls can be bought at Harken dealers or ebay. Simplest and fastest is to fix the flange, not the sheave, in a vice
Pry gently with a screw driver
Remove steel flange and insert balls. Make sure you hold everything together or you will be looking for balls on the floor, and they are ridiculously expensive per ball.
What is left of the balls…...
Vice it back together and you will plastically deform the tube edges so the flange sticks. I have done 6 sheaves this way, no problems, just be gentle when prying and when “vicing” it back so you don’t mess up the edge of the center tube.
Jeanneau Sun Odyssey 51 - Anders Flodin