Inline 6 Cylinder Exhaust Manifold to Head Gasket | Sierra 18-2830-1 Combination intake & exhaust manifold gasket fits Mercruiser GM straight 6 cylinder marine engines. Exhaust manifold gasket Fits Mercruiser GM inline 6 cylinder marine engines Replaces Mercruiser 879036, 27-52584, 27-33121, 27-46401 Replaces OMC 907932 Replaces Osco CY6-GH Replaces Mallory 9-61416 Replaces Sierra 18-2830