Fisherman looking for boat will pay diesel

Why not support a local business and take a charter?

Which island? If STT I may have a suggestion.

Just be aware that legally, if you are paying for fuel, this constitutes a charter and therefore the operator must be a licensed captian with the appropriate insurance and license.

Not trying to be a stick in the mud, but there are folks who have all the overhead of operating a legal business and it's unfair for them to be undercut by illegal operators. We should be encouraging these businesses and supporting them.

That's not entirely true. It's not the act of paying for fuel that would tip the scales to make this a charter. Anyone can share costs with a friend if you are having an outing together, whether a road trip where you chip in for gas (this does not mean he has to be a licensed taxi driver) or a flying trip where the passengers chip in for actual fuel costs and landing fees on a island hopping trip with their buddy in his small plane, or a boating trip where people chip in on fuel. It's where there's a set fee and/or a profit being made that the chartering aspect starts to get sticky.

Think about it, though. If you really want to go to Buck Island and your friend has a boat but is broke and can't afford gas, you can volunteer to fill the tank if he'll take you out there. A shared cost experience isn't legally a charter from what I've been taught in my Captain's classes.

When a stranger is seeking a boat to take him fishing, yes that sounds like a charter. There's an element of what the relationship is between the parties that sets the tone for whether it's truly a charter or if it's two friends on an outing where each contributes in a different way, one with equipment and the other with fuel.

The question of at what point an individual becomes a “passenger for hire” has caused confusion but is very straightforward. “Passenger for hire” means a passenger for whom consideration is contributed as a condition of carriage, whether directly or indirectly flowing to the owner, charterer, operator, agent, or any other person having interest in the vessel (46 CFR 24.10-1). Therefore, requiring strangers to share expenses constitutes a passenger for hire operation.
“Consideration” means an economic benefit or profit including payment of money or donation of fuel, food, beverage, or supplies. It does not include a voluntary sharing of the actual expense of the voyage (46 CFR 175.400).
If a vessel carries just one individual passenger, or “hop on,” who provides anything more than a voluntary sharing of the actual cost of the trip, the vessel is operating as a passenger vessel and requires a Coast Guard licensed operator. If more than six passengers are involved, the vessel will require certification as a Coast Guard inspected vessel, as well as a licensed operator. In other words, if the owner, charterer, operator, agent or anyone else who has an interest in the vessel receives any money, fuel, or supplies that the passenger did not freely choose to share as part of the actual cost of the trip, the vessel is carrying a passenger for hire and must meet the following requirements:
(1) The master in command of a passenger for hire vessel must be an individual licensed by the U.S. Coast Guard

This is a direct copy and paste from a USCG notice quoting CFR 46 and explains the situation in question.
Of course it does not explain the question or ethics of taking away business from a working, licensed operation.