Composite timing chain cover without sensor port mounts to the front of GM small block marine engines. Timing Cover | Sierra 18-15480 Composite timing cover for GM 5.0L 305 CID and 5.7L 350 CID marine engines with no timing sensor hole Includes front seal and timing cover mounting gasket Replaces Crusader R004010 Replaces Mercruiser 835005 Replaces Marine Power 804007 Replaces OMC 3856594 Replaces Volvo Penta 3856594