Where can you find information about 18th century sea routes and sailing times?

OK, be prepared to do alot of research.
1. check the newspapers of the time they will have info about what ships are leaving and comming in and most importantly WHERE they have come from.ie; " Today the Vanilla arrived from England by way of America, south America." as you can see these are short. one line nuggets of info, but if you are dilligent you can get the "by way of's" together and form a mental cruse from poit A to B. Times may not be included as ships will come and go with the tides.
2. next you find navigational charts. modern one are ok as long as they have wind directions, and sea currents. KNOW the time of year as well, remember if the north Atlantic is "warm" in July, cape horn is miserable.
3. ships tend to wreck in the same places during good weather so in finding sites of 18th century ship wrecks one can see or pick out a probable route.
4. remember this stuff only applies to ships and routes during PEACE. warships are out completely as printed information from the day is usuially false. During war civillian ships were targets of privateers. so they might choose a diffrent or unusuial way from A to B. BUT we are creatures of habit and the sea is dangerious so us sailors stick to KNOWN, SAFE,& FAST routes.
good luck