[PaulK]

Not sure exactly what you are calling the jib outhaul. There’s a jib sheet that attaches to the clew, and then a traveller for the Hoyt jib boom. Looks like 1/4” or 3/16 would be enough on a boat with a jib that size. Perhaps looking up Harbor 20’s for sale and checking the pictures would give you an idea of how others are rigged and how long the lines need to be. Has the current line you have chafed through? Rotted away? This might also be helpful: https://www.youtube.com/watch?v=UMr5XshIHkA