Your friend is right, assets purchased for the business using business funds is separate property. Especially given that the business was started way before you were married.

However; assets purchased for personal use, such as your car, furniture, the house you live in (if it was purchased through the business but after you were married) is marital property. He can claim that it is a business asset, but then he would have to explain why you are driving the car, living in the house, using the furniture.

To be honest, if his business doesn't involve boating in any way, then the boat isn't separate.

You are better off discussing this with an attorney.

Another thing that you will want to keep in mind is that your stbx could be purchasing personal assets through the business so that he can claim them as a business expense. That won't fly with the IRS if they ever do an audit. During the divorce process, you want to make sure that this is addressed as the IRS will hold you personally responsible as well.