I own a L185F also. There is some confusion that you may have.
The tractor has the overrun clutch built in. This is a "ratchet" device inside the tractor that will dive the PTO in one direction but let the implement free wheel when the clutch is pressed in. In other words you can stop the tractor with the clutch regardless of the implement you have. The PTO will be "disconnected" from the drive when the clutch is pushed.
There is an add on device for (really, really) old tractors.
See this video (thank to forum provider!)
http://www.youtube.com/watch?v=k5-XUE09by4
There is a second type of device that is a slip clutch that reduces the possibility of damage to the PTO drive train and the implement. These are add on devices (sometimes they could be part of the PTO shaft of the implement). They are a pack of springs and friction plates that will slip if the torque requirement is too high (locked up implement, tiller into rock, mower blade into a stump...) You do not have to have one of these but it will help protect the implement and the tractor if you maintain it.
I have a L185F. The operators manual is available from Messick's. It may be available from the dealer (I would try there first since the Messicks is a photo copy). I have it in PDF if you want it that way (send a PM and let me know your e-mail address).
Here is how the clutch works on the tractor. If the PTO is not engaged, push the clutch in, put the tractor in a gear (hi or low speed range also selected) and release the clutch. Off you go, just like almost everything else in the world.
If you want the PTO engaged (in gear) and not move the tractor; push the clutch in (tractor should be stopped) and put the PTO selector into gear (1=540 PTO RPM, 2nd and 3rd are higher speeds you will probably never use). Leave the transmission gears in neutral. Release the clutch and the PTO will start turning. Stay away from the engaged PTO - it wants to kill you and is always trying to come up with a new way to do it!
IF you want to combine PTO and movement; Push in clutch, put both transmission and PTO in gear. Release clutch and you will move and the PTO will rotate. Push in the clutch and the power is removed from the PTO and the transmission. You can
For example when I am using the shredder (brush hog, rotary cutter...) I will set the engine RPM to the mark on the tachometer (~2500 RPM?) put the PTO in gear, transmission in neutral, release the clutch and the shredder will come up to speed. Push clutch in, put transmission into gear, release clutch and off you go mowing! To stop just push in clutch and the tractor will stop but the implement will take a while to coast down to zero RPM.
Hope this helps and is not too much useless information.