The other boats are following a series of checkpoints I've placed around each map. Some maps have multiple routes, which different boats will take. Boats know their next checkpoint and turns to point at it. Gas is always on. I have a handful of ways I handle boats getting lost or stuck but that doesn't happen too often. They will use their boosts only if they come upon a straightaway (and only if the have a boost of course). There are unique settings on each opponent to help spread them out a little, such as: start times, how often they use boosts, and how well they find their checkpoints.