Im looking to purchase a boat soon, either a new tracker 190tx (20,000) or a used boat in the 10-20k price range. what kind of loan % rate should I expect for great to excellent credit? I'll either be trading in or selling and putting roughly $4500 down.

Depending on the lender, you might see a slight difference in the rate from new to used. Some have no difference at all. MOST rates are starting around the 5% and above. We do see a few JUST under but that also depends on the term. SOME lenders offer a bit lower rates for shorter terms.
Let us know how we can help.
Ken

Im not sure of your credit score / Debt to income, but with a 20% + down payment like your talking about, you should be able to get a really good rate. I recently refinanced my boat down to a 3.99 through my credit union. That was a similar situation, I only financed 80% of the boats value. SHOP AROUND you should be able to come up with a good option depending on your credit. There is another post talking about 1.99 at City CU. mine was at Tinker FCU and im pretty sure 3.99 is pretty much the best they will do. Good luck

Somewhere in the low 4's with that down payment