I can lower it but the next adjustment puts it just under the hook... the boat is off balance for some reason, one side is higher and I need to replace one of the middle rollers as it's got chunks out of it.
will have to play with the position and see if I can get it on a good spot.
And no, no Nylock nuts that I can recall... will check when I get home, I used the hardware that came with it as everything was still pretty much spotless, no rust or damage visually.