what is going on with my brisket?

I have a masterbuilt electric smoker,put a 15.5 lb brisket on at 3 am,temp at 250 ready for a long cook.check back at 8am and the temp is 205,how can a 15.5 lb brisket be done in 5 hrs?

Certainly doesn't seem right unless you wrapped it. Usually 1hr/lb at 225

did not wrap.

Did ya eat some?

Thermostat may be bad

Check the thermostat by putting an oven thermometer or other thermometer in the smoker.

Nothing wrong with having it done early though. I've held briskets for 12 hours before keep them warm in a cooler of food warmer.

No way its done even at the Masterbuilt max temp of 300°. Get a handheld thermometer to check for brisket doneness. In five hours, I doubt its even hit the stall.

How did you check the internal temperature of the brisket? One, you might not be getting the temperature probe in the right spot. Maybe that temperature probe is off. Boiling water should read 212.

No way a 15# brisket gets done in 5 hours at 250. I cook at ~250 and the time is around 50 minutes/pound.

it was done in 5hrs and it was good. will stand by my first post,this is not my first brisket,all others were smoked on a side fire box,and it would take 12,15 hrs

[/quote]it was done in 5hrs and it was good. will stand by my first post,this is not my first brisket,all others were smoked on a side fire box,and it would take 12,15 hrs
[/quote]

Congratulations, you just figured out how to smoke a 15.5# brisket in 5 hours and have it turn out good. Masterbuilt electric smoker, set at 250, 5 hours, internal 205, got it.

Sounds like you pressure cooked it

What grade beef were you using? Choice and Wagyu tend to stall. Prime has the shortest to no stall at all. I've cooked 15lb briskets anywhere from 6-20 hours depending on the stall. Example: last year i cooked five 15lb Prime briskets for my daughter's graduation party. The first one reached 193 degrees (my done temp for Prime) in six hours, the last took appx. 13 hours. I was worried about the six hour brisket until i served it. All five tasted pretty much the same. Equal in tenderness, moisture, flavor, bark quality, and smoke ring. I rarely cook choice, so I'm no help there. Wagyu can stall for as long as four hours around 175, but when it comes out it will reach finish temp quite quickly.

[/quote]it was done in 5hrs and it was good. will stand by my first post,this is not my first brisket,all others were smoked on a side fire box,and it would take 12,15 hrs
[/quote]

I've been cooking briskets for almost 30 years and cooking competitively for over 10. I'm familiar with how long it takes to cook a brisket. I realize different grades will cook different and smokers cook different. Cooking a 15 lb brisket at 250 unwrapped takes longer than 5 hours regardless of the smoker. Either you trimmed the heck out of it so it was more like 7 lbs before you cooked it, your thermostat is wrong or it wasn't done. I'd be checking my thermostat. Also if you don't have a quality thermometer to check the internal temperature of your food that is a must have.

"Also if you don't have a quality thermometer to check the internal temperature of your food that is a must have."

This is also very accurate. You should have a remote probe in every piece of meat. When it gets close to your done temp, check the brisket in several spots with an instant read. When doing this, you can also gauge for tenderness by how easily the probe slides into the beef. If you have to use more than very light pressure, keep cooking

I place a block of wood right under the center of the brisket. I started doing this to help the juices run off to form a complete crust over the entire brisket. I discovered by watching how the brisket droops over the block when its close to being done. I still use a thermometer to corroborate.

Sounds like you indulged in a few too many brewskis when you put it on and forgot about a 5+ hour nap you took.

Congratulations, you just figured out how to smoke a 15.5# brisket in 5 hours and have it turn out good. Masterbuilt electric smoker, set at 250, 5 hours, internal 205, got it. [/quote]

This ^^^^^

Maybe UFO's had something to do with it?