A couple of weeks ago, a friend and I visited a local marina to price some replacement props for his new Mainship 40 trawler. While he was engaged in the technical stuff, I strolled over to the "Prop Knocker" display. How could you pass up a name like that?!
Anyway, the marina owner strolled over to chat about this product, swearing that it was pretty much all they ever used at this mostly power boat marina, and that it handled the big boys with ease.
I later found the
Prop Knocker on the Internet. The price list doesn't go below a one inch shaft, but I don't see why the concept wouldn't work with a smaller shaft (Just use a smaller "knocker", right?).