I changed my water separator on my 5.1 mercruiser, I accidentally filled water separator with 40 to 1non ethanol fuel and installed. Question is will that fudge up my motor
The water separator will be refilled with straight gasoline, as you run the motor. So it will initially run on that 40::1 mix, and then the oil in the mix will lessen quickly.
I always ran some 2 cycle oil in my MerCruiser fuel. It seemed like it was good to have some oil running thru the cast iron intake manifold, to keep the rust down.