Yep, this is a favourite tactic of mine. I don't tend to bother with the lighthouse, instead I just build several galleys. If you are careful with the exploration you can get most of the way round the world for the cost of just a few. One important thing to remember is that you only stand a chance of losing a galley when it ENDS it's turn in ocean or sea. Hoppoing a gap won't be a problem. If you can't get across in on turn, send three galleys, one is lkely to get through. Once you contact one civ on another continent, you'll get the maps for all.
Preaching to the converted here I guess, still it IS a good tactic.
Racing across the ocean on a large map in my one ricketty old caravel dirrectly after constructing the Great Lighthouse, I was naturally the first civ to make contact with one of the other large continents. And suddenly I found that trading in World maps to be the most lucrative deals ever! Trading for a few hundred golds a turn plus a modest down payment and contact with other leaders. Lo, before long I had hawked my ever increasing world map around every civ, letting it grow larger each time, and made not only a massive profit but was receiving so much gold per turn that the boom years came early to Brentford (the English capital under my exacting megalomaniacal regime). If only I could have built Flappers as a military unit and constructed The Great Gatsby as a minor wonder...
