engine hesitation

[switchme]

I had a problem this weekend with my engine hesitating and basically running rough. Then at apprx. 3500 rpm it starts making a loud knocking noise. It will jump approx. 500 rpms with out touching the throttle. I have a 04 marine power gm vortec 315hp mpi. I checked all connections in the engine box and no fix. The engine was just in for its 100 hour service a week ago. Any ideas before I haul up to the dealer would be great.

[Tige M.D.]

look under the thread 5.7 gm vortec problem. i explain how to check the low psi fuel pump. during the service a mechanic may have knocked it loose.