My book says you need a rope 68 1/2 inches long. You should have a manual to follow but i did it without one the first time. Basically you remove the recoil assembly and then very carefully remove the plastic piece the rope connects to without letting the spring unwind. Put the new rope on and tie a figure 8 knot and fuse ti with a flame. Wrap the rope around the pulley counter clockwise (looking at it from the top)and from there you should be able to figure it our for yourself or (best bet) get a manual. The spring is visible once you take the plastic piece off so make sure you have a good look at it and see if the loop end has broken (the sometimes do if the rope breaks) If the spring comes unwound it will attack you so wear glasses and clothes that are for getting dirty. Best of luck. Rick.
Edit: Here is a must read for anyone who has a 9.9. Loaded with information. http://www.sschapterpsa.com/ramblings/OMC/OMC info.htm
They are needed only if you need to replace/rewind the spring. Assuming it is not broken, be very careful separating that plastic spool from the spring. It is a very easy job if the spring remains wound. If it unwinds or needs to be replaced--not so much!
