Yes you must remove
the centerboard to replace the line. I did mine while in the water. What a pain!!! I did not have an air supply and the parts must be aligned to get back in place so I did a lot of huffing and puffing. Dropped all the parts twice and had to go down and find them. I was anchored in about 6 feet of water. If while your boat is in the water you take the centerboard bunks off the trailer, then load the boat on to the trailer I think you might be able to lower the board far enough to access the rope slot. I,m going to modify my board bunks so they can be removed with the boat loaded.Replace the line before it breaks; for your safety and so you'll have a line to pull the new line in with.By the way, do you have the small tackle system in place in the up-haul?