If you are buying something on credit, it is just as important to negotiate the interest rate as it is the price. The interest rate can save thousands, if not tens of thousands of dollars over the course of the loan depending on size of loan and how many years involved.

I let the sales person know that I needed a 5% interest or no deal on the boat I was looking at after a price was worked out. She came up with a 5.25% through a credit union.
They have sources they work with to make the deal--- it's their job.

In your case where you appear to be looking for a loan yourself, I wouldn't rule out a credit union. Some have a niche in the boating industry.