The centerboard tackle has developed a desire to twist the last couple of years. I've crawled into the bilge and untwisted the lines a few times but now the Quad Sheave (page 42 item #7) has been scored by the line and it remembers where to twist and cut into the side of the block. I'll have to replace the block but was wondering if anyone has put in any kind of guide to prevent the block from twisting or know of a way to keep the up/down line from getting twisted as you raise and lower the centerboard?