I'm not sure if this works with emulators (I guess it could if you use two), but when I was a kid and I was playing Pokemon Red (while my sister was playing Pokemon Blue), to get where you are, I had to trade with her/she had to trade with me a pokemon with Cut CS (number 02 if I correctly remember), this way, it was useless to beat Gary in the boat then looking after the captain, and the boat was at the same place during all the game, thus, you could surf up to the truck.
I don't know if you already did that too.