I posted a reply to your comment in the Welcome To The Exmark Forum thread. You stated that the engine was overheating when you cut tall grass. My earlier response referred to the "1/3 rule"(never cut more than 1/3 the total height). After reading your comment about the uncut blades of grass I'm still thinking that part of your problem is letting the grass get too tall before mowing. If you are allowing the grass to get 5"-6" tall and cutting it at 2.5" that could very well cause the problem you are describing here.