From IRS publlication 936
For you to take a home mortgage interest deduction, your debt must be secured by a qualified home. This means your main home or your second home. A home includes a house, condominium, cooperative, mobile home, house trailer, boat, or similar property that has sleeping, cooking, and toilet facilities.
Second home. A second home is a home that you choose to treat as your second home.
Second home not rented out. If you have a second home that you do not hold out for rent or resale to others at any time during the year, you can treat it as a qualified home. You do not have to use the home during the year.
Second home rented out. If you have a second home and rent it out part of the year, you also must use it as a home during the year for it to be a qualified home. You must use this home more than 14 days or more than 10% of the number of days during the year that the home is rented at a fair rental, whichever is longer. If you do not use the home long enough, it is considered rental property and not a second home. For information on residential rental property, see Publication 527.
IRS specifically mentions RV and Boat. Also 14 day requirement only applies if you rent it out.
I just get an interest statement from bank and include that amount as Mortgage Interest that I do not receive a 1099 for... whichever line I don't know. I use H&R Block software... as it allows me to easily include some other deductions.
