Same disclaimer as everyone else, as I'm not a tax professional, but I do my own taxes as honestly as a can with TurboTax. The IRS allows ONE second home, which CAN be a boat if it meets certain requirements. I verified this myself not only with TurboTax but also on the IRS website, and you probably should too if you do your own taxes. So interest on boat loans are deductible as a second home for FEDERAL taxes.
Boat-as-second-home deductibility varies from state to state, however. In Wisconsin, boats may NOT count as a second home, so I have to make "state adjustments" to my deductions on my state return since Wisconsin uses the federal return as a starting point.
After owning two boats, both of which were financed, I have never gotten a Form 1098 from my lender. I have to get the "interest paid in xxxx year" info separately from the bank, then declare it on Schedule A and indicate "I didn't receive a Form 1098 from this lender."
And no, tax deductibility was not a factor in my purchase decision (it rarely is)... just a VERY nice break.