Anyone?? Probably everyone has gone through this whether it was new or used, unless they paid cash. Your credit rating will also influence how much deposit the finance company/bank would want with a minimum of 10%, usually.
Just about any finance company will give you a yes or no "pre-approval", rather quickly. The age of the boat will influence the banks decision too.
When I bought my used Regulator, I called a finance company that specializes in boats/marine financing. I gave them all the boat info and price. They called me back the same day and said that they would do it and required 10% down. The dealer asked for 10% down for a sea trial anyway. I did the sea trial, signed the papers and owned the boat two days later.
My credit is very good and my debt/income ratio is very low.
I ran into my "rep" from the finance company at the Palm Beach Boat Show. I told him I was looking and actually considering making a move on a 190k rig and he told me he'd do it, no problem, with a big smile on his face.

I gotta stay away from those shows.................

at least until I'm really ready.