Took the boat out and ran fine cruising 3200 rpm at the end of the day I opened it up and barely gained from 3400 to 3800 where it bogged and sounded like it backfired out exhaust. Throttled back to cruise and ran fine. 2001 5.7 vortec Marine Power. 233 formula center console. When I got home I checked if the timing was advancing and it idled at 8* but only advanced to 12* while revving. manual calls for 26* total. Any help would be appreciated. Thanks