It's either North on 19 till you hit 54, take a right - and go down the road for about 20 miles, Marathon will be on your left.

Or you take 275 North to 75, take the exit for 54, and travel west to collier, the Marathon gas station will be on your right. You can google it if you want:

http://www.google.com/maphp?hl=en&q=...16,0.1157&om=1