Near the end of the Venice boat chase, Kazim pulls out a gun and shoots the engine of Indy's boat, allowing the two boats to come closer together. The engine explodes in a cloud of smoke.

Indy jumps onto the Kazim's boat, and starts punching Kazim. The boat then gets chopped up by the propellor of another boat, and Elsa comes to the rescue: In the boat with the broken engine! After that they drive the boat to the nearest pier!

We saw what happened, and Elsa's boat even came to a stop! It is impossible for it get going again so quickly! No way!