I recently purchased a new boat and had it financed. I went with a Tracker Pro Team 175TXW so I can only speak from my experience with going through Tracker.
I was required to put 10% down regardless of my credit. The tag, registration, etc.. was all wrapped up in my deal so I had no out of pocked with the exception of the down payment and boat insurance down payment. I do regret not upgrading to the best trolling motor I could get but the one that came with it works for now. I would say get the best that you can comfortably afford.