Boats Gotta Go, how do I get rid of it?

[Rightbrainer]

Try Boat Angel Ministries
https://www.boatangel.org/

[SVTatia]

Do you have title to the boat?
Whether or not you do, you'll need a recorded/signed transaction, don't just mail the key as you said.
If it falls in the wrong hands and they don't pay the slip fees, or worse, do any property damage, you are liable. Just saying.

[Fbfisher]

And just like that, he’s vanished. Moving on...