We had those things, PowerWinch brand, for years. The really old ones had a ratchet to keep the boat from rolling back on retrieve and that part was a maintenance problem, along with the disk clutch itself. Later models used a one-way needle bearing that would fail to two-way and let the boat roll back.
So: Use a supplemental turnbuckle arrangement to hold the bow to the stop and don't rely on the winch.
We had issues with the electrical, where the cord from the truck plugged into the winch. If the ground failed, it'd smoke the trailer's lighting harness looking for an alternate ground.
So: Unplug trailer lights to use the winch.
We also found the winches were very optimistically rated. There's a double-pull arrangement (pulley at the bow hook) but that really slows the retrieve and also worsens the pulling ratio because there's so much more cable on the spool.
So: Buy one that's rated for about twice what your boat weighs.
You could try posting a Want To Buy add here at BE. Without an anchor you'll have to post email or phone, though. I'd buy a used one from somebody I knew and told me it was a working unit. The ones we had weren't very well built to begin with so I wouldn't call them a good used-sight-unseen product. If you feel lucky, Harbor Freight sells one...