Installation Manual
Chapter 2 N38143
Page 8
Dry systems
Dry exhaust systems are most commonly used with engines which are keel cooled and are used for
environmental reasons in some areas. This arrangement is particularly useful for commercial or pleasure craft
operating in heavily silted water with debris and with radiator cooled engines.
Dry exhaust systems for marine installations need careful design to minimise the disadvantages of enclosing
components that are at a high temperature in conned spaces. A typical system is shown in (F).
The rst part of a dry system should include exible connections (F2) to permit movement between the engine
and the xed part of the exhaust except the 415GM and 422GM which have a simple ange (F1) for the
customer to connect to. 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. Fitting a second bellows (F4) 90 degrees to the rst will achieve this.The bellows
and elbows should be covered with re blankets (F3).
The remainder of the exhaust system should be well insulated to avoid re risk.
If there is a long exhaust run which gains height as it leaves the exhaust manifold, it may be necessary to
incorporate a trap to collect condensate and allow it to be drained.
Minimum bore of the exhaust pipe
415GM
40mm (1.6ins)
422GM
422TGM
700GM
4GM
60mm (2.4ins)
4TGM
4.4GM
4.4TGM
4.4TWGM
76mm (3ins)
4.4TW2GM
6TG2AM
6TWGM
Bellows should be in an unstrained condition when installed, so that the full bellows movement is available to
absorb expansion and engine movement.