Thanks for the save, it's very helpful!
First off, games with this many players are going to take a lot of time, there is no getting around that. Games on huge maps are going to take more time as the AI tries to figure out safe paths for each fleet over longer and longer distances.
Looking at your save we see the following:
ResetOldPaths 32s (seconds): this is each fleet recalculating the path to its destination
CheckForEndOfGame 16s: checking to see if anyone has won a research victory
CalcInfluence: 55s: lots of tiles on the map, lots of players influence to calculate
FindPath 81s + 37s: calculating the path to numeorus potential destinations around the very large map
UpdateObjectList 44s: go through and validate all the game objects
UpdateCivList 18s: go through and validate all the civs
I did test both for zooming off the map to see if it reduced turn time (it didn't with this save) and disabling combat particles (which didn't with this save). As well as noting that the time spent in the above functions wouldn't imply that either of those would be causes (in this case).
This definitely gives us some data to look at optimizing. We will never get this large of a game ot be as quick as a more normal sized game. But I bet we can make a serious dent in these times.
Thanks again for the help, we have some wok to do!