One other item, if you have a smart phone, link your card to your phone in the google wallet or ApplePay system. Any time your card is authorized, you will receive a notification for exactly how much, when, and where.
Back to the OP, marinas will increase the authorization to $250 because of the cost of fuel at a marina, usually an 80-125% markup from the nearest gas station on land. Why? Because lakefront property isn't cheap and they have bills to pay.
Ignoring the cost of the the property, imagine what the insurance costs for on-the-water fueling! Selling gas, either on land or on water, isn't much of a money maker.