I just bought the Torpedo Jet Ski at core city and after trying to enter a different area on the Torpedo I got an "Error: Zone Transition Failed" message. I tried this with every other Jet Ski and didn't receive a zone transition error. After a long time of trying different things it seems that I can only enter a different area if I don't have a secondary engine in my Torpedo.
Parts:
XG Power 4.0
BArm Medium Jet Shocks
XG Alpha 3.0 x 2