I’m actually in transit these days, slowly making my way across the country (Canada), back to the boat. So my net access is limited. But I’m really not the guy to consult about engine stuff. My level of expertise is pretty low.
There are lots of real experts online here at CF though. You should start a thread asking about the problem, or dig through the old ones. You’ll get get info, I’m sure. I know I have when I’ve had Perkins problems.
Just FYI, our 4108 seems to run at around 160 F, which is about 70C. Sounds like you’re definitely running hot.