A heat shield for an internal combustion engine used in a boat, or other application where engine compartment heat is unwanted, has a water cooled body positioned around, but spaced apart from, the exterior surfaces of the exhaust manifold of the engine. The concavity of the heat shield body fits the manifold and engine closely, to intercept and carry away radiant and convective heat. The shield is held in place by means of a boss which is captured between the exhaust manifold and the exhaust pipe of the engine. The shield enables industrial engines to be adapted to marine use without re-certification to meet environmental regulations.