Saturday morning went to the Aurora and it had dumped the entire contents of the radiator on the road. I had never seen such green antifreeze before. I had a gallon of 50-50 and poured it in and followed it up with 3/4 a gallon of water. Drove the car about 10 miles to my mechanic. The engine ran under 200 which was a total shock to me. After discussing it with my mechanic, he said that too much antifreeze and not enough water can cause an engine to run hot. So try increasing the water content of the cooling system - it may help out.
My mechanic is going to replace all rubber in the cooling system and fix the leak and put in the correct mixture of antifreeze to water. Hopefully it will run within normal temps.
Without knowing the history, or even the condition of why it boiled over, it's very unlikely the mix ratio will have such a significant effect. There are other issues at hand.
It's true: anything over 67% coolant will raise the temperature. The best cooling is with the least amount of "coolant". However a cooling system additive, such as Redline' Water Wetter (or the the like), will significantly lower coolant temp (via reducing surface tension, which aids heat transfer).
My Aurora boiled over (and shouldn't have), while on the car lift during semi-hot weather, after a short while of testing, also losing about 1+ gallons-- a joy to clean up. Added the Redline product and so far so good, but I still need to diag the cooling fans and verify the ECT temp with a scanner. If the fans are working, then it's probably time for a new T-stat, but not a "colder" one, just one that works properly.
If your car has a cooling problem, replacing the hoses won't fix anything. If the coolant was very low, fixing the leaks, of course will help. Hopefully neither of us has a cracked cylinder head. Your mechanic can use a gas sniffer or other test apparatus to confirm, by verifying excessive HC counts in the cooling system. Fingers crossed on that one!
Let us know what your tech finds out.