My buddy has a 2012 250 Pro XS that recently shot a rod, therefor causing it to fail. Upon taking it to a local mechanic to do the warranty work in putting a new powerhead in, the mechanic told him that this is not covered under warranty because he was running premium gasoline.

The reason the mechanic gave him for the motor failure was the fuel to air ratio.

The question I have is, should I not be running Plus or Premium gasoline in my Mercury? Could this cause it to over heat?

I was always told to run the highest grade gasoline in my outboards.

This is posted on the BBC, not sure if it will cause an overheat.

FUEL:
-All models- MAXIMUM ETHANOL CONTENT: 10%. Ethanol content may adversly affect engine performance.
-See "Mercury's View of Ethanol" on Sherm's board at: http://www.bbcboards.net/mercury-mot...nded-fuel.html
-Standard Opti's (ALL) 87 Octane MINIMUM.
-Standard 2-stroke Carb/EFI Models: 87 Octane MINIMUM.
-XS, XB or Racing PRIOR to 2006- CONSULT OWNER'S MANUAL! Most require High-Test!
-ProXS and 250XS 2006-UP: 87 Octane MINIMUM. IF poor idle quality occurs, could can try 89 Octane (mid-grade) to see if quality improves.
-300XS- Consult Owner's Manual. High Grade (minimum 91 Octane) fuel required!

Don`t think so. Only warranty issue I am aware of on fuel is 15% or more on ethanol. Premium fuel leaves more carbon requiring a carbon cleaner like Sea Foam in the fuel except for Chevron. They have techtron (ring free)in there fuel. Carbon is death to a 2 cycle motor if left untreated.

read this.... go to tha "fuel and oil" part.... know several that run 91/92 exclusively in pro xs's with no warranty problems...it might apply to non ethanol fuels... 87 is minimum.... that mechanic is full of it!


https://dmna.ny.gov/nynm/manuals/Mercury_250_OptiMax_Manual.pdf