Not sure how the Coasties currently view things, but there was a time when their interpretation of the law was that accepting any compensation for taking people out on your boat made you a "for hire" operator.
Certainly, if you demanded being paid in any way by your passengers, you ran the risk of running afoul of the law. Much better to let your passengers "offer" to share expenses.
This strict view of what makes one a "for hire" operator may have been eased a bit, but you might want to look into it anyway
