TPD1317e Chapter 3 Due consideration must be given to providing flexibility in the exhaust hose, particularly if the engine is flexibly mounted. Where the exhaust hose must pass through a bulkhead immediately behind the engine it is preferable that the arrangement shown in Figure 3 is adopted, using rubber bellows to provide flexibility. Note that the bellows should be in an unstrained condition when fitted. For turbocharged 6 cylinder engines, use a single double hump bellows where space is Point of water injection to be 200mm (8 inches) For turbocharged 6 cylinder engines use silicone rubber restricted.
minimum height above water line bellows 5 o minimum average fall Figure 3 - Movement of the engine on the flexible mounts must not be restricted by the exhaust hose. Use rubber bellows as shown where space is restricted. 3.2 Dry Systems Dry exhaust systems for marine installations need careful design to minimize the disadvantages of enclosing components that are at a high temperature in confined spaces. The first part of a dry system should include a flexible connection so that excessive weight is not carried by the connection to the engine.
Connections of the stainless steel bellows type are suitable, but care must be taken to ensure that they are only required to accommodate movements that do not involve twisting the ends of the bellows relative to each other. The remainder of the exhaust system should be well insulated to avoid fire risk. If there is a long exhaust run which gains height as it leaves the engine, it may be necessary to incorporate a trap to collect condensate and allow it to be drained. Figures 4, 5 , 6, 7 & 8 show typical systems. The minimum bore of the exhaust pipe should be 76mm (3 inches) for turbocharged engines, 63mm (2.5 inches) for naturally aspirated engines. Page 13