Use a heavy stiff line
I now use an old, I mean old and stiff three strand, 1/2 inch nylon dock line as my painter. This line will not droop down, if it's stiff enough, and get caught in the prop. It is about 12 or so feet long. I have strong metal terminations on each end. Heavy S/S snap hooks with swivels would be good. I just added my input to the "have you ever wrapped your dingy painter around your prop shaft ? " poll.My input was "yes". worse yet, it came undone with relative ease. But, I believe that in the process, the painter was nicked and subsequently parted. The dingy came free never to be seen by me again.That painter was new light (about 1/4 in.) nylon. When I anchored for the night on that occasion, the dingy came close to the boat (as usual) and the painter drooped down. In the morning when I pulled the anchor and prepared to leave anchorage is when the loss of the dingy was set up.I now use the stiff, heavy nylon painter. Not as much strech as new nylon, but not as much droop, either.Merrill