Is this way too much or is that possible?
Yes, those stats do seem high. However, if your are lean, and were working reasonably hard for an hour it definitely possible that you were approaching 1000 per hour cal expenditure.
I think its reasonable to assume you could average 185bpm for an hour, so if you want to adjust your HR to reflect cals more accurately you can input a different "setup weight" into the watch.
Perhaps setting the weight value to 150lbs will provide a more accurate value.