I would never intentionally damage someone elses property - then you are no better, perhaps even worse as they probably didn't know any better, and didn't mean to run over your line. It still ***** people with no respect or knowledge of water ettiquette are allowed to operate a boat on public water.

I think the line around the prop, eventually eating into the seals, would have been enough lesson. If he didn't have the common sense to respect someones space on the water, I very seriously doubt, he will check his prop and shaft for stuff like that - my guess is he will need a new lower unit in after a summer's worth or running with water in lower unit oil.