here ya go guys , at least its from my Mercury mfg on that subject when i asked about my motor.
-------------------------
Thank you for the recent inquiry regarding your Mercury 25hp EFI engine,
serial number 0R#####. We appreciate the opportunity to respond to your
question.
Your engine is designed to use fuel with up to 10% ethanol. Since ethanol
is an alcohol, if there is water present in your fuel tank it could
separate from the gasoline and mix with the water. If this happens you
would be running on fuel with a lower octane which could cause damage to
the engine. There is a section on our website that talks about ethanol.
The web address is
http://northamerica.mercurymarine.com/serviceandwarranty/outboardfaqs/ethanol.php
We hope this information was helpful. Should you have any other questions
or concerns, feel free to contact our office at 920-929-5040 between the
hours of 7:30am and 4:30pm, Monday though Friday, CST.
Sincerely,
Mercury Outboard Customer Service