Turns out that the outmoded idiom, "slow boat to China," is actually an old poker term. A card-shark finding a whale (dead money to you land-lubbers) would tell him that he'd like to "get him on a slow boat to China." There's no specific boat in mind. Indeed, the phrase was most likely used by east coasters or south-westers, nowhere near the necessary ports of call.

http://www.straightdope.com/mailbag/mslowboatchina.html

(p.s. The idiom got me riffing on the irony that our language contains an idiom about how slowly we travel to the very country with which we have the largest trade deficit. It's as if, in a Shanghai cafe, one should expect to hear businessmen on deadline talking about putting their work "on the hydrofoil to Frisco.")