Any boat over 15 feet (I think) is required to be equipped with a blower to vent the engine compartment. It's probably just a very small squirrel cage blower & electric motor. It may even come with some of the duct pipe.
I'll look on the SeaDoo to see just how big it is.
Here is a sample of what I'm talking about:
http://www.outdoorsuperstore.com/pro...OWER&cat=62202
It's about $30.00 and uses 3" ID hose.
One of the reasons that this set up would be ideal is that it is already marine grade & designed for mounting in the engine compartment. Water ain't going to hurt it & it's designed to operate in a potentially explosive atmosphere so those pesky gas fumes aren't a concern.