SILENCERS

We manufacture each silencer as a bespoke unit. 90% of our production is dedicated to individual craft. Each silencer is built by a team of two craftsmen working to an ISO9001 accredited quality management system, and to the requirements of the major classification societies.

Careful attention is given to achieving the accuracy of angle and dimension agreed between design staff and client to produce systems which will fit precisely in the given space. Inlets and outlets are skilfully positioned to couple to the engine and to the rest of the exhaust system. Each completed silencer is tested at five times operating pressure before being gel-coated.

There are two types of silencers within the range - Lift Silencers and In-line Silencers - and the use of each type is dependent upon whether the engine is positioned above or below the waterline. Lift Silencers are designed for use with engines positioned on, or below the water line, and In-line Silencers are used where the engine is well above the waterline.
 

Lift Silencers
HMI Lift silencers are designed for use with engines positioned on, or below waterline. Thousands are sold each year and major users include most quality British production boatyards where excellent acoustics and good temperature resistance are paramount. HMI Lift Silencers are as popular with generators as they are with propulsion engines. There are various configurations with the range of Lift Silencers from side in/top out to top in/top out and from end in/end out to twin inlet dual chamber configurations for V engines.
 

Side In, Top Out Lift Silencers - up to 50% noise reduction
The side in, top out lift silencer is the best selling small lift silencer in the HMI range. Smaller silencers have smart, resin transfer moulded lids. Every unit is pressure tested and gel-coated for a durable and smart appearance.

Top In, Top Out Lift Silencers - up to 50% noise reduction
In many applications a top inlet unit will be easier to use. The noise result and cost are the same as the side inlet units, and the same rigorous quality tests apply.

Horizontal End In, End Out Lift Silencers - up to 50% noise reduction
These low lying units can be very useful in sailing yachts, where the silencer needs to be secured alongside the propeller shaft. The moulded ends are used on smaller units.

Dual Chamber Silencers - up to 80% noise reduction
Some dual chamber silencers have two inlets to accept the exhaust hose from a V engine. Each inlet has been specifically angled to suit the particular craft and the outlet points straight to the positioned provided on the hull.
 

In-Line Silencers
Halyard In-Line silencers are used where the engine is well above the water-line, or where a high-riser has been fitted to achieve a 1 in 8 gradient from the engine to the transom outlet. They are simple to specify and fit, and ideally need to be 500m to 1m behind the engine. The internal design requires the exhaust gases and water to bubble through a layer of water on the bottom of the silencer to reduce noise. They offer excellent noise reduction and are widely used on both pleasure and commercial engines.
 

Round In-Line Silencers - up to 50% noise reduction
These silencers are made from enormously strong filament wound tube, giving the maximum possible protection if the exhaust back-fires. Every unit is pressure tested before being gel-coated. They must be installed within 5 degrees of horizontal.
 

Oval In-Line Silencers- up to 50% noise reduction
Our oval silencers are hand-moulded for use where the round body unit cannot be accommodated. They give the same excellent results and every single unit is pressure tested and gel-coated. Halyard Twin Inlet In-Line Silencers are built on an individual basis for V engines. The inlets can be angled to ease the connection to the engine, and positioned on the end or the side.

Dry Silencers
Dry silencers are used with wet exhaust systems, or as a stand alone system, to achieve agreed noise attenuation and back pressure. Each unit is designed for a dedicated application, from stainless or mild steel, and supplied pressure tested. The best acoustic results ever achieved have resulted from our dry silencers down-stream of the engine, feeding a water injected exhaust system or Halyard's unique silencer separator units.
 

Dry Silencers
This example of a dry silencer has been manufactured specially to suit a "V" engine, with two inlets which connect directly to the turbo outlets.  A single silencer outlet then feeds the quieter exhaust gas into a water injection system followed by a conventional Halyard wet silencer, achieving a superb acoustic result.