Your lender probably won't care about anything except a survey--to be done to their specification--and a clean title transferring to you. If the boat is documented the title is tied to that process. If it is state registered, there may/not be a separate title and registration, depending on the state and the age of the boat.
The purchase agreement, no matter how informal it is, should also state that the transfer is being made free and clear of all liens, etc. to you, just in case there are any mechanic's liens or storage liens that you aren't aware of. The lender may be able to suggest a title company or someone to handle the sale details for you, as well, but a lawyer can be a good idea when there's any major dollar value involved.
Hey, I've got this great Sundeer 65 that's stuck in Nigeria, I just need a couple of grand to pay the port fees and once I get it back to the US you can have it for a song.