I was mistaken about the temperatures, this is what I found with a thermometer...
45C - Continued submersion no problem
50C - Can stand a second without pain, two seconds I'm gritting my teeth, 4 seconds and I'm screaming
55C - Can stand one second, and that hurts
60C - forget about it
My finger can stand maybe 5 degrees more than my penis, surprise. I've found it's really hard to be burned, I pushed myself up to my pain threshold and a little past it but it doesn't seem like it's even close to actually burning me.
It does seem to be helping get rid of the whiteness though so I'm going to keep doing it.