I used my old boat as a second home. almost 100% of the interest was tax deductible . It had a cabin with a bed and toilet (portapotty). Coleman stove (in the garage)for cooking if they asked. Sold it for a cat, no cabin, no nothing!!!! No more tax right off. Not sure how you could use it as a business expense. My accountant was against it!!!! At least not in my line of work, and not with my boat.