running 89 Octane in a 2004 250XS

[ucf_motorcycle]

I have twin 2004 250XS that call for min 91 octane. I can get reasonably priced 89 octane fuel ethanol free on the water, but I don't want to damage my engine of course.

I called mercury racing to see what the difference was between an 06 (which can run 87 octane) and my 04. They said the compression was higher in my engine. I asked if I swapped to the newer heads would that allow me to run lower octane fuel and they were not sure and couldn't help me further.

Anyone know if I can do something to be able to safely run the 87 or 89 octane?

[Tom Foley]

Don"t do it or you will have a rebuild thread , just run the e-10 93 octane !!!!!!!!!

[WILDMAN]

Last customer I had that ran 89 in his 300xs, blew it up!

[ucf_motorcycle]

Copy...I wasn't going to try it without modifying whatever needed to be changed in order for it to run safely like the 06's. Is there anything I can do to run it safely?

[arrowwaves]

Just run the 91!!! I once got 20+ gals. of 89 and my motor hated it. 2003 250XS The guardian wouldnt let the motor run more than 3500 rpm's. pumped it out and replaced it with 93 oct and it runs fine. I use 93 because all that was available at the docks was 89 and 93 now 93 is hard to find so I fuel with cans from the gas station but I still use 93 much fresher than the gas dock also.