The leak is more likely from the pump rather than the motor.
Isolating just where the water is coming from would be my first tact. If it's not at a hose connection, it may be a crack or defective seal in the pump casing. (Was it subject to freezing temperatures and did you winterize it?)
If there's not a manufacturer's service center around you, you might try a small engine (i.e. lawnmower) repair shop.

Here is a link that might be useful: Briggs and Stratton Pressurewasher Manuals OnLine