Re: prop lock problem
No lock--and this includes prop locks--is theft proof. What the lock actually does is make it easier for the thief to steal the prop on the boat next to yours, or it makes him take more time than he wants to, to remove it. Remember, The thief wants to do his deed fast and get out. Hanging around gets him caught.
You, on the other hand have all the time in the world SO: if you don't care about damaging the prop lock, try drilling two holes in the top like on a deck gas cap, put two pins in them and then try to twist it off with something.
OR---If you have a really good friend with a welder, weld a nut on top. Or even try epoxying the nut on in the hopes that the lock is not on too tight.
OR: ---go to Home Depot and buy a sink wrench--it's made with about a foot long handle with a tee on one end and a crescent shaped grabber on the other. It is not too expensive. It is made for installing and removing sink faucet nuts. It may slip on the chrome but you should be able to figure something to stop that.
See: that's just three ideas-with a little thought and some thinking outside the box, you will get it off without too much fuss.