Tractor Repair: Overheating, red zone, coolant

Question
I have a 3cyl. MF that at 52 hrs. was run without any coolant twice.

I first time was from 15min. to 2 hours, the time frame given to me was "a while".

The second time was only 5 minutes but the meter peaked past the red zone. I was present.

Prior to this the "Normal Temp" ran on the 1st line of the meter during the hottest part of the day.
After: "normal temp." is 1/4" aove that line.

What is the probable damage?
How would this affect the life of my engine?  

Answer
Overheating can cause numerous problems including - block - head warpage - ring failure - bearing failure - engine internal parts becomming brittle.  The results of overheating are normally not immediatly identifiable - but the life of the engine will be affected.