Check the fans in the case, make sure they are functioning (obviously one or more of them are not functioning) and replace them with working fans.
the fans kick up and get loud and there doesnt look to be a problem with any fans
Does this mean you checked them all, or are you just reporting your previous observation about the fans?
This is not a problem with LR. It is a problem with your Mac computer as it is not cooling the CPU and GPU sufficiently even though the fans are running at there highest speed.
Check to see what else is running on your system. Shut them down when using LR.
Check to make sure there isn't any dust clogging the air vents of your Mac.
Don't use the Mac on a soft surface as that can cause the heat to build and block the air vents.
How long ago was the logic board changed and did the problem happen right after the board was changed out or did it take weeks/months for the problem to show up again?
I have a similar problem with lightroom making my late-2011 macbook pro run hot. It doesn't shut down though. What I've added to my sytem that seems to help a lot is a small utility program called Temperature Guage pro - https://www.tunabellysoftware.com/tgpro/