Bought a 1988 Sea Ray Weekender to try my water camping experience. Had the Manifolds, Risers, One head, Water Pump and all oils replaced when purchased. Took it out for a trial run in fresh water. Engine runs great and smooth when not engaged with the outdrive. When in engaged runs smooth to 2000 RPM then backfires and pops. Got it up to full throttle on occasion but after backfire throttled down to 2000 RPM and ran smooth.