Specialty marine lenders. These are firms that know boats, aren't
afraid to accept a boat as collateral (iow-won't tie up your house in
most cases), and exist in a competitive environment. Wherever you
finance, make sure you compare. Make sure that "sweet!" deal on the new
boat itself isn't offset by less than competitive but oh-so-convenient
financing.

Here in the Pac NW, we have marine specialty lending companies like
Essex, Trident Funding, Seacoast, etc.
There are undoubtedly similar companies but perhaps with different
names in your area.