Mig, if a boat is spawning instead of a boxburg, I would think you have some kind of corruption or file error somewhere in your game...simply using someone else's save file will not help. I'm not a coder so I can't say for certain.
You also didn't say if you were using other SA mods, which are of course, incompatible with TTDiSA.
Your best bet is to uninstall the game completely, then reinstall from the CD, then install the mod and use no other mods. Be sure you're using an english version of the game, and that you aren't using warez / crack to install, or else the mod probably won't work.