Are the Life lines in good shape?
There could be many reasons the old ones don't fit but if the cable is in good shape, you can cut them, resize them, by replacing the swaged fitting on the cable side of the turnbuckle. Johnson Marine makes a Johnson Lifeline Stud ( 1/8" and 3/16" cable size not including the cover) hand crimp fitting that is easy to use. The cable goes into the stud far enough to crimp the stud in two places. The Johnson Lifeline Stud ( hand crimp type ) costs about $6.00 to $10.00 each You would need two. The Hand Crimp Tool is about $40.00. So, for $60.00 and some of your time you could save $250 (that is if you have a 25' boat.) Then again, if the old life line shows wear, replace it.You will need to note left or right hand thread. If you need more detail, let me know.r.w.landau