Mercruiser Stainless Steel Thermostat Housing | Sierra 18-1989 Stainless thermostat housing fits various Mercruiser GM 4.3L, 5.7L, 7.4L and 8.2L marine engines. Fits various Mercruiser GM 4.3L, 5.7L, 7.4L and 8.2L applications Stainless steel construction Includes inserts, pipe plugs & thermostat gasket Uses Sierra 18-1989K gasket service kit Replaces Mercury 87290A4, 8M0061381, & 861006A1