Honda engines are designed and certified to run on regular unleaded gasoline.
Gasoline is allowed, by regulation, to contain a variety of additives. The same regulation limits how much of some additives, such as alcohol, can be included in the fuel and still allow it to be sold as gasoline. If you look in a Honda product owner’s manual, you will see that a maximum of 10% ethanol is allowed in gasoline (other oxygenates are also listed). Honda engines are designed for good performance and efficient operation using gasoline containing from 0 to 10% ethanol.
E85, a mixture of 85% ethanol and 15% gasoline, has been in the news recently. E85 is an alternative fuel; it is not gasoline. Honda Marine engines are not currently designed or certified to run on E85 or any other alternative fuel.
Always refer to the owner’s manual for your Honda to get a list of recommended fuel and the current approved additives.