Wow, trying to wrap my head around the weights listed on that cut chart. A steamship round only weighs 50-60lbs and it's the entire round, top/inside, bottom, eye and sirloin tip and a large hunk of the femur. A whole top/inside round will probably weigh between 12-18lbs.
Cooking time won't be dependent on weight, but rather, on the thickness of the loin. While the round might be 16 inches long and 10 inches across, it should flatten out and be about 5-7 inches thick. At 225ish, figure on about 5 to 7 hours. Also, instead of having just one big piece of meat on the kettle, you might think about splitting the round right down the middle with the grain. This will make it easier for you to arrange the meat for indirect cooking and protect it from direct heat and will also make it easier to slice against the grain later. Cooking time won't be affected by cutting it in half as long as the thickness is still the shortest dimension.
If you can, I'd definitely recommend cooking this at low temps. I used 225 above for timing, but if you could get down to 200 or even lower, it will be even better. The lower the cook temp with this cut, the more tender it will be.
I also have to disagree with Buckie on this one.. If you want to do a sear, do it at the end. Take the meat to about 120 degrees internal and then roll it around to develop a crust.