Is it time to sharpen my lawnmower's blades?

Hi. I own a 1991 Craftsman Lawnmower and whenever I mow the gr, the engine slows down and then stalls. I have checked the gas tank many times and it is more than half full, so that isn't the issue. I was wondering if this could be an issue related to the dullness of the blades. Should I sharpen them?