OVER RUNNING CLUTCH- QUICK DETACH: Yanmar Tractor Parts This allows the implement pto shaft to continue to spin even though the tractor pto has stopped.
Rotary mowers, sometimes called bush or brush hogs have a flywheel inertia that will push your tractor forward after you push the clutch in which can be dangerous. Some pto implements like a tiller does not have that flywheel inertial so it might not be necessary to use the over run clutch with it but certainly no harm in using one.
tractorErnie, one of the Yanmar guru's on this forum has always recommended the use of an over run clutch, especially on the power shift models. Not only is safety involved with the over run clutch but also the bang that can happen to your differential when shifting the power shift at high speeds when mowing. Not good with words but hope I have explained well enough to convince you to get an over run clutch.