So I kind of had a bad feeling when I started making the starter for my IPA on Friday. Brewing Saturday was very spastic to say the least, and I am pretty sure there were gremlins in my equipment. My digital probe thermometer went wacky, and did not match up with my other two thermometers (actually all 3 were different, but the probe thermometer was WAY off).
I was shooting for a mash temp of 153º so I preheated the MLT, got the strike water up to 166º, added grains and the temp was about 149-150º. So I had some boiling water ready to go, and added a little (maybe 3-4 cups?), stirred and called it good. 90 minutes later when I took the lid off my MLT, the thermometer inside said 158º!!! So I overshot by 5º. I did a double batch sparge and collected my 7 gal of wort OK, but my efficiency was only 70% and my OG was under what was predicted.
What effect will a 158º, 90 min mash have on my beer? Is the high mash temp the probable cause for my low efficiency?