I know this is not the answer you are hoping for... but may I suggest you pull the boat out of the water and take it to a repair facility? In the short term this will be the fastest and the least expensive way to solve your runability issue. Swapping out parts based on suggestion always costs WAY more than it should and also takes longer to find the cause. A good tech should be able to diagnose your problem accurately within just a little time ( ;
Need LT-1 parts?
OIL FILTER: Factory installed is a Penzoil P23, Afta market brands, AC Delco PF-454 and a Fram PH-13 or PH-30 will work.
SPARK PLUGS: AC Delco MR43LTS (gapped to .040")
FUEL FILTERS: AC Delco 25171391 (pump inlet side)
89058397 (pump outlet side)
IGNITION WIRES: Call Inboard Online @ (877) 327-7175 and order part numbers 556010A (odd bank) and 556010B (even bank)