A catamaran can qualify as a second home for tax purposes and you can take the interest on your loan as a mortgage interest tax deduction on your personal income tax return. In order to qualify as a second home, the debt must be secured by your main home. In addition the multihull has to have sleeping, cooking and toilet facilities.
A yacht, such as a catamaran, can be used as both a personal recreational use and as a rental use at the same time. If it can be shown that the boat is used for business or rental purposes, it is extremely important to keep a detailed log of the entire use of the boat and the related expenses.
In such a case, the rental activity is not considered a passive activity for income tax purposes, and as such, the losses are limited to the income. However, additional losses not used may be carried over to the next year. If the catamaran is used for both personal and business, you must meet the basic rental test of renting out the boat for more than 15 days during the year in order to qualify as a rental use.
Having met the test, you can now take a percentage of allowable expenses, including: mortgage interest, advertising, insurance, repairs and maintenance, and depreciation, etc.. against the rental income on your personal income tax return.