TOPIC: 1961 Merc 400 Operating Temp

I got my 1961 400 running in a tank but felt it may not be cooling correctly. Hard to tell if the new water pump is pumping the volume it should when the water/exhaust exits under the cavitation plate. I was getting very little water out the the exhaust relief tube on the back of the drive shaft housing. I also noticed there is no exhaust release baffle in the drive shaft housing. I am hoping my year/model may not have come with an exhaust relief baffle and if it came with one, do I really need it to make the motor run/cool properly?
I wanted to monitor the temp of the block while the motor runs to make sure it's cooling correctly. What are the tempo readings I would get at the cylinder head using a touchless temp gun?