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Engine Exhaust Systems  

During the operation of any marine engine- gas or diesel- exhaust gases are produced and must be removed from the engine and conducted outside the boat.

While there are two basic exhaust systems, wet and dry, the wet system is the one most often found in pleasure boats as well as many workboats. This system mixes the exhaust gases with engine-cooling water and then discharges them through the transom of the boat via an exhaust line.

 Exhaust Manifold

 Attached to the engine is an exhaust manifold with its exhaust inlets matching the exhaust outlet ports of the engine. Circulating cooling water through the water jacket surrounding the exhaust gas chamber cools this manifold.

 Exhaust Connector

 At the exhaust end of the manifold is an exhaust connector. This connector is an intermediary between the manifold and an exhaust hose or pipe. This connector also mixes the exhaust gases with water to further cool the gases, and it operates as a means for directing the gas and water outflows so that a connection can be made between the manifold and the exhaust tubing.

 Particular attention must be paid to the relative height difference between the center line of the exhaust end of the manifold and the center line of the transom overboard exhaust fitting, the exhaust connector can be exhaust dump or drop of a convenient angle.

 In those instances where the manifold is not appreciably above or is below the overboard fitting, an exhaust riser is used. By design, the riser acts as a dam to keep both exhaust-cooling water and seawater from back flooding into the engine and destroying it.

 Back Pressure

 From an engineering viewpoint, the most critical design requirement for exhaust systems is to limit the backpressure on the engine to a minimum. Backpressure is the pressure that builds up in the exhaust manifold engine exhaust outlets. The lower this pressure, the more efficient the operation of the engine. Low backpressure is achieved by designing exhaust passages to minimize resistance to the flow of gases and to prove for a uniform gas flow away from all cylinders.

 Barr manifolds and exhaust connectors are designed to minimize backpressure. In many cases, after replacing an OEM manifold with Barr replacement parts, more r.p.m’s are achieved.

Replacement Exhaust Systems

 When the need arises to replace an OEM-installed manifold and/or exhaust connector, one of the three situations will exist: replacement of both manifold and connector, replacement of the manifold only, or replacement of the exhaust connector only.

 When replacing both manifold and connector, normally there are no problems in matching, and connection to existing exhaust lines is usually very easy. When replacing just the manifold or just the exhaust connector, problems can arise in matching the replacement part to the existing part. Barr recognizes these problems and, wherever possible, has provided the necessary adaptors for connecting a Barr replacement manifold or exhaust connector to original exhaust parts.