My mac macbook pro 2011 model A1278 came with a 60w charger. Can i replace it with 85 w?

Yes. See the quote below from Find the right power adapter and cord for your Mac notebook - Apple Support

Power adapters for Apple notebooks are available in 45W, 60W, and 85W varieties. You should use the appropriate wattage power adapter for your Apple notebook. You can use a higher wattage adapter without issue, but doing this won't make your computer charge faster or operate any differently. Lower wattage adapters will not provide enough power.