So much for the theory. Now let's work our way through an exhaust system, starting at the engine end and look at some practical issues.

Taking care
Exhaust components are designed to withstand big variations of temperature and pressure, but GRP is relatively brittle and can be cracked or chipped if dropped on a hard surface or bashed about with metal tools. So it makes sense to treat them as carefully as possible during installation.

Access
Although a well-designed, high quality exhaust system will last unattended for many years, it makes sense to make access as easy as possible. Building a hatch into the back of a locker or cupboard is a minor job compared with ripping out whole sections of furniture at a later date to tighten a leaky hose clamp!

Risers
The first part of many exhaust systems is the riser. This should be firmly supported with a stainless steel saddle bracket and struts -not left to hang from the bolts securing it to the engine exhaust manifold. The supporting struts must be attached to the engine or gearbox, not parts of the hull structure, or engine movement will fracture them in short order.

Flexible connector
Attached to the riser, or to the exhaust manifold directly if no riser is fitted, is the flexible connector. The connector plays a vital part in absorbing movement between the solidly mounted exhaust system and the flexibly mounted engine. if a piece of normal exhaust hose is used, it should be long enough to absorb vibration and cope with the engine's normal movement. if this can't be achieved with straight hose, a flexible bellows must be used.

An exhaust bellows allows lateral and fore-and-aft movement between the engine and the fixed exhaust system.

If the flexible connector goes through a bulkhead immediately behind the engine, sufficient clearance must be provided to ensure it can't touch the bulkhead even during maximum lateral deflection of the engine. If very soft engine mounts are used - with a Halyard Aquadrive system, for example - the clearance may have to be as much as half an inch.

Installation Tips