True that means you can not afford it. Here are some numbers and facts. To start off with your going to go 20 year in for a boat that is already 13 years old? You really going to keep it till its its 33 years old?

If you go 20 years and your rate is say 5% which I think is probably better than you will see but you will pay 329 a month you will almost pay 30,000 in interest in that boat. Does that make sense??? If your going to do this at least do a ten year you will only pay 13 in interest and your payment will still be low 500's.
Your best bet is to save up 10-20k and take a 7 year loan out max. You go the route you are thinking you will be upside down on that boat forever.

Michigan first CU, 7.49% up to 250,000 and up to 240 months. High performance Ok, and they are very very lenient with the age of the boat.

Citizens community federal