This is my second Formula that's had this problem. The generator surges after being run for 5-10 minutes. It's a factory installed Kawasaki generator. It starts and runs great for the first 5-10 minutes then begins to surge real bad.

Sounds like the choke is sticking.........open the hatch and mess around with the throttle stuff.....

Could be something wrong with the engine RPM governer too.
For that you may need to contact a service tech.

I'll look and see if the chocke thingy and if not, off to a pro!

I had the same issue with my (factory) 5kw Onan. Replacing the fuel filter didn't help, but changing the spark plugs worked like a champ. Most generators get run under too light a load, and tend to foul up the plugs.

I think you could be right! I'll give that a try.

My generator was acting up and the mechanic told me as soon as the engine starts running rough,change ou t the plugs first!

Dukenrock - What fixed it in the end?

I haven't seen the boat since I posted! I hope to get to it this weekend. I'll let you know if the plug takes care of it.