have twin 575 sci and both engines are fouling the back four cylinders. Does this come from starting in cold weather or running slow at night?

Are you still on the factory tune? If so, I'd suggest you find someone to put in 02 bungs and tune on the water. Our old boat with 575's ran like a top - both at idle, cruise, and WOT - after Eddie Young tuned them.

You may have other issues, however - leaky injector, etc. ...which Eddie Young can fix you up on that as well.

Good luck!

575s are pig rich at idle no matter what, have the ecu flashed and be done with it. This a common question here and have lived it with my 575. Eddie young, Mark Boose?, Ben Weirsom of precision power, amont others have can flash them. They will have a canned tune that works if your engine is stock.

Who leaves a 575 stock? They are really 700's, just missing a few pieces.