I know this is a very old post, but I finally got around to installing a probe-type thermometer in my EFM's flue pipe. With the thermometer installed about three feet from the flue outlet, and just before the baro, I observed 105 degrees F with the boiler resting (25 minutes since last timer cycle). After 20 minutes of stoking I observed 275 degrees F. After 30-45 minutes of stoking it was up to 315 degrees, and seemed to plateau there. All readings were taken with the boiler water at approximately 150 degrees. The heat exchanger was cleaned about 3 weeks ago, and the stoker is running 4 teeth, 4.25 air...burning rice.