Looking up, you can see the nozzle of the shotgun on the ledge of the 2nd floor window; pointed towards your boat! BLAM! BLAM! Thankfully, all the shots seem to miss. Jennifer must not be good at long distance shooting.
"Crap!" Fumes Diane, "That crazy cow knows what's up. I'm going to rev this thing faster."
She speeds up the boat and brings it out into open water. Unfortunately, her efforts seem to be exhausting the boat's fuel supply. Furthermore, the gold in the boat adds extra strain on the boat, making the craft heavier.
Overall, the elements contained on board contribute to the reduced performance of your boat. In the distance, you can make out another boat, with two figures on board quickly gaining towards you.

Say something to Dr. Dragon or Tobias
Call out to other boat
Use rope to swing to other boat
Start throwing gold overboard
Ask Diane to do a loop-dee-loop to confuse them
Ask Diane to turn back, to again, confuse them