Marine grade type A is a fire-resistant hose, it withstands a 2.5 minute direct flame, plus it is certified to not allow more than a specified amount of alcohol fumes permeate the rubber line. It should be used inside the boat from the tank to the transom in a 3/8" I.D. Auto gas line does not have to meet those safety specs.

Type B marine hose is not fireproof, but still is certified for alcohol use and is suggested for the transom to the motor.