I agree! I was lucky enough to borrow money for myself for my new boat. I sold mine myself before I bought the new one so I knew exactly how much I had to put down on a new one. Now granted life without a boat is tough, especially this time of year, but at least I knew what kind of dept I would have. I would say if your boat runs fine then keep it until you pay it off then sell it. It will allow you to put some money down on the next one and not be so upside down!
Ex. I financed 11.5K on my last boat for 5 years. I paid it off in 2.5 years and kept it for 5 years total. It allowed me to keep paying myself a note to a savings account for 2.5 years even though I was dying to buy a new larger rig I didn't. I found a guy selling a Cert he won in a tourney for 18k and I upgraded to the 175xs for $2,200. With all the extras, tax, dealer delivery charges I ended up spending right at 25k for my new boat. I sold my boat for $7,500 had saved another $5,500 over the 2.5 years so that means I only "self financed" $12,000 on my new boat that I will try and pay off in 2-3 years again. I don't like having a note tied into a boat eventhough I fish a good bit.
Anyway I hope this helps.