These shutters are designed for the following MerCruiser applications: 1996-1999 V6 owners PLEASE LOOK AT PICTURE #3 Note: These will NOT work on V6 engines that came with the one piece manifolds (Use 807166A2 it has a flat tip), or early V8 with the round pin going through flapper. Used on many MerCruiser sterndrive V8 engines. (Some V6 that came with the two piece maniflold/elbow) For 1998 and newer engines, there are some 1996 and 1997 models that apply. There will be two rectangular holes for the grommets. If your Y-pipe has round holes you need the A3 water shutters. If your Y-pipe changes size a few inches bellow the shutter you have a one piece manifold V6 Y-pipe and need shutter A2.