Boat, 1996 Bayliner Jazz Jet

1996 Jet boat with new short block. Motor has about 30 hours on it and runs but bottom cylinder will not fire. All cylinders have 125 psi and spark. I believe it is a carb issue but I don't have time to look at it.. This is a very nice clean boat, I sure someone knows these boats very well and could fix easily or part it out. The reverse grate is on the boat and in good shape.