So my mash temp was a little hotter than I wanted and added to much cold water (1.5 quarts). Checked it after 10 minutes and it had fricken dropped into the low 140s. Just added 1.5 quarts of 185 and it’s holding now. My question is how much will this jump in temps affect my beer.
The answer depends on a few things, how hot did it get and for how long. If you got it down to the low 140’s fairly quickly, your probably OK. All of the enzymes won’t denature instantly, it takes a bit of time for that to happen. When all is said and done, you really won’t know until you take your FG reading post fermentation. Who knows, this might turn out to be your best brew yet… and then you gotta figure out how to do it again! 
Since you don’t mention how far you overshot and how long it was at any temp, I can’t say how it will affect it. But it’s done, so don’t worry about it. Write down what you did and wait for the end results, that’s all you can do at this point.
If it was just a little too hot & you immediately dropped the temp to the 140s,let it sit there a bit then brought it back up, then congratulations, you almost mastered the Hochkurz mash method, Infusion Mashing - German brewing and more
I can offer only a single data point, but your experience mirrored my second batch almost exactly. It was a regular Keystone Cops exercise in incompetence. I was overzealous when pre-warming my mash tun and ended up with my mash at 166. Panicking, I stuck my chiller in and managed to get it to about 140 faster than you can drop a carboy on a concrete patio. I then added very hot water to get it up to the mid 150s, where I made my first smart decision of the day and quite effing with it. This was on March 16.
I’m down to my last 4 bottles of it, and sorry to see it go. It came out great, and me and my friends have enjoyed it. The process is surprisingly tolerant of beginners mistakes.
I bet you’ll be just fine. But please let us know-- this is how people learn.
Just have some ice ready next time - I overshot into the low 160 range and stirred in ice cubes to get it to 156 in a minute or so. By the end of a 90 minute mash it had fallen to 146… It appears to be fine for a dark lager. I hope you didn’t hit 170 - which is pretty much a mash out temp.
Well I think next time I am just going to add a little less than I think I need. It’s always easier to add a little at a time. You can’t really take anything back once you’ve added to it.
+1 to ice cubes. Works pretty quick.
you have to figure out your equipment and then you’ll be able to nail your mash temp constantly. for me, i’m basically about 10F hotter than my desired mash temp.
+10,000 for ice
The phase change from 32F/0C ice to 32F/0C water requires almost as much as energy as does raising the same amount of water from 32F/0C to 212F/100C. It takes 334 joules of heat to convert one gram of 32F/0C ice to one gram of 32F/0C water (latent heat of fusion for water). It takes 418 joules of heat to raise one gram of water from 0C to 100C.
And let’s not forget that your ice is starting somewhere in the range of 0F/-18C, so it will absorb some heat on its way up to melting temp as well.
Joules Bergman or Crown Joules?