I don't think the 6517 could run a tiller. The PTO engagement lever has a spot for mow and ST.
Was a good mowing tractor for me. I replaced one spindle and pulley on the deck when it kept shearing the pulley hold down bolt on the right side. Also about 6 drive belts 2 of which was in 2013 and with in minutes of each other.
Replaced the hydro drive belt twice the last just a couple months ago, Rebuilt the steering drag link when it was 2 years old. no problem since.
Engine has had ignition module changes on the third one now. A fuel pump and the normal oil changes and plug changes. One starter solenoid too.