Found out mash thermometer was broken after the boil

This should be interesting, I brew in a bag on a bayou burner in a 10 gallon pot. This is my first weizen and I was having trouble with the mash, according to the thermometer it was 150 exactly but after 90 minutes and a drop to 148 I still was testing positive for a tiny bit of starch via an iodine test. I figured maybe wheat just has some unconvertable starch and started the boil. I noticed the thermometer went to 217 during the boil and thought maybe some extra heat was coming around the outside of the pot. Then chilling was taking forever and pretty much stopped at 100 degrees, but the pot felt cool to the touch. I grabbed a laser theremometer and it tested at 68 degrees while stirring, it was that cool. Thermometer still has not moved

Original gravity is 1.050, 65% efficiency, I have no idea what temperature I mashed at, it should be interesting to see where it ends up at. Are you supposed to not leave the thermometer on during the boil or recalibrate it regularly? Should I pitch it or just adjust the screw on the back? It's a Winters model, tsw series, goes from 30-250 degrees, sits in a thermal well above the kettle valve, it's been very accurate for 6 batches and I stopped double checking it because it was never off before.

I had a thermometer issue a few months ago. I don't have the same set-up as you as I use a digital thermometer and just manually insert it into my mash or wort, wait 10 secs and record, but I don't see why you cannot leave your thermometer in the wort as it is boiling. I am building a brewstand now and I don't plan on removing my thermometer from my kettle after I install it. Everyone swears by ThermaPen for accuracy and durability, but that pretty much negates having a thermometer built into your kettle or HLT or MLT. I had a dial thermometer that caused me problems, so I just bought a digital that I calibrate every other brew.

It's not in the wort, it's on the front of the brew kettle.

+1 for thermapen. I have dial thermos on my HLT and bk. use the thermapen to make sure they are calibrated and to check my mash temp. Thermapen is a great investment.

I might have to spring for one. Fermentation is going like crazy, hopefully all is well.

It's down to 1.007 so I'm guessing the temp was lower than 150, all is well but now I will be a two or 3 thermometer guy. Thermapen is on the way.