Perhaps a simple question, but I am wondering how people lock off their prop shaft while they are charging their batteries under sail. If I put my transmission in neutral while sailing, the shaft spins like mad. I typically put the transmission in reverse with the engine off to lock the shaft with the folding blades closed.

I would like to lock the prop off to charge the batteries, but in a way that can easily be overridden if I need to engage the engine in an emergency situation (i.e. without having to go below, undo something from the shaft, etc.). Any ideas?