I have a Kohler 5E marine generator, I was doing some PMs on it and tested the voltage output and is was putting out 145 volts. The manual states it's a 120 volt output unit. Any idea?

Hi,
Often the unladen voltage and RPM of the engine on a generator are above spec. Most generators have a 50 RPM governor "droop" per 1kW.
Here is a link to Kohler Power Marine technical document:
http://www.kohlerpower.com/marine/technicaldocuments.htm?sectionNumber=13461&nodeNumber=3&contentNumber=301 (http://www.kohlerpower.com/marine/technical documents.htm?sectionNumber=13461&nodeNumber=3&contentNumber=301)
Peace,
Clarke