My 75 gal lp gas hot water heater is dripping water from the hole in the side of the heater that the pipe (overflow?) comes out of. Is this something that can be fixed?

It sounds that you have a leaking T&P valve see the image below also for information regarding the T&P valve open the link below.

T&P valves are installed for safety in case the water temperature or water pressure goes high it will open to depressurize the water tank, also some times the valve will leak if there is any mineral deposit built try to lift the small lever and drain some water and close the lever see if will help, if not you need to change the T&P valve, if will need to change the T&P valve come back and we will tell you how to change it, good luck.

John

Temperature and Pressure (T&P) relief valves - Support - Water Safety & Flow Control -Watts

We need more information then that, Shut off the power and open up the upper inspection panel, Is the insulation wet above the hole? Can you see what's leaking? A threaded joint? Leaking from the top connections? Give me something to work with. Back to you, Tom

Sorry I think I miss read the thread, any how please respond to Tom, Thanks.

John