What is the oil to fuel mixture for a 115 horsepower mercury outboard engine?

Probably 50-1 is the correct mix, but! You do not provide the year, so I suggest you call your local Mercury dealer to be 100% sure. Fuel/Air mixture is critical. Also ask about which octane fuel you should use. it may require 89 octane fuel.

Probably 50-1 is the correct mix, but! You do not provide the year, so I suggest you call your local Mercury dealer to be 100% sure. Fuel/Air mixture is critical. Also ask about which octane fuel you should use. it may require 89 octane fuel.