Patent ID: 7726120

Claim:
A marine engine exhaust system defining an exhaust passage extending from an engine exhaust manifold inlet to an exhaust system outlet, the exhaust system comprising: an exhaust manifold configured to merge multiple exhaust flows into a merged exhaust flow; a catalytic conversion element disposed within the exhaust manifold to intercept and catalyze exhaust flowing through the exhaust manifold; wherein the exhaust system also defines a raw water coolant passage extending from a seawater inlet, through the manifold to a coolant exit open to the exhaust passage downstream of the catalytic conversion element, such that seawater is injected into the exhaust within the exhaust system; wherein the coolant passage extends between the catalytic conversion element and an adjacent external manifold surface, to remove heat generated by the catalytic conversion element and avoid excessive manifold surface temperatures; and wherein the coolant passage is spaced from the engine cylinder head.