Insulating the engine compartment

Insulation for engine rooms and engine covers 
An engine room that leaks noise is a complex problem. Noise and vibration can be heard and felt in and around a vessel in several ways. The issues can be dealt with well once you detect the place where noise and vibrations are leaking. Some places to investigate in order to discover noise leaks include:

How to insulate engine noise in a boat, yacht or ship?
When the hatches and walls are well isolated, no noise leaks, heavy insulated decking and floors, it is generally only a matter of insulating the walls and ceiling of the engine room, or engine cover or hatch. This is best done with noise absorbing and soundproofing products, we have presented them below. Make sure to cover all surfaces in the engine room or compartment with the right product for the job. Try to apply the thickest product possible, thick product absorb low frequencies from the engine best.  

Which products to use in an engine room or compartment
Products for large engine rooms, low temperature:
  • Merfocell PU: up to +80 °C, with an oil- and moisture-tight top layer.
  • Acousticcell PU: up to +80 °C, with an oil- and moisture-tight top layer.
Products for small engine rooms and compartments, high temperature:
  • Merfocell FC: up to 110°C, insulation with fiberglass cloth.
  • Merfocom: up to 100 °C, combined product soundproofing and absorption.
  • Flamex FC: up to 150°C, can only be used on flat surfaces.
Tips for boat insulation 
Guides to insulate pleasure crafts and ships can also be found on our Tips page: Boats and Yachts 

Acoustic products to insulate an engine room and engine compartment:



Place sound insulation and sound absorption in your boat's engine compartment

Sulating the engine room
The engine room is often adjacent to other rooms such as a sleeping area, wheelhouse or aft deck. The engine noise is best stopped by insulating walls and shutters by providing them with Isomat TS (or for larger projects with Isomat KE). These plates can be glued with Saba Select glue (use 0.5 liters/m²). For extra good fastening, we recommend using some flat-head screws on the corners of the plate.

Sound isolation, in the form of mass plates such as Isomat, works particularly against the low frequencies of engine noise. The best result is achieved when the mass of the walls and/or shutters can be doubled. Make sure that the insulation boards connect seamlessly so that there is no sound leak


After the application of sound-insulating products, a sound-absorbing material is applied to "extinguish" the sound from, for example, the engine, compressor or other sources. In an engine room there is generally enough space between the engine and the absorption material, heat is not a problem here. Acusticab, Merfocell PU or Flamex PU , the latter product can only be applied to flat parts! Here, too, the plates must connect well to each other to prevent sound leaks. Tape the seams between the plates with AcustiTape so that no moisture, dirt or dust can penetrate it.

Sulate the engine casing
In many pleasure craft, especially in sloops, the engine is shielded by a casing. This is often a "box" placed over the engine. The material of this box is often lightweight, for example thin plywood, and therefore does not block much noise. Also, the engine casing often does not connect to the bottom of the vessel which then forms a sound leak.

The easiest way of insulating is to provide the inside of the casing (box) with Merfocom. This combi plate consists of several layers and provides both insulation and absorption. You can also put together products yourself in order to achieve the optimal insulation for your situation. Provide the casing inside with Isomat TS (the heavier, the better) and finish this with an absorption material of your choice. If there is little space (-10 cm) between the motor and the absorption material, use Merfocell GW or Flamex GW. With a spacious (+12 cm) casing you can use Acusticab, Merfocell PU or Flamex PU. Instead of combining products, you can also only use absorption material, for example in a renovation job.

Attention points
Prevent sound leaks through cracks and seams, but make sure there is sufficient ventilation / cooling for the engine. Silent ventilation can be done by making a labyrinth through which the air is supplied or fed. You line this labyrinth from the inside with Acusticab 13mm thick. For example, air can go to the engine, but the sound can hardly go out.

Another way is to use the Aluphon damper. An aluminum tube with a 25 mm thick wall that is perforated inside and filled with an absorption material. If there are already ventilation facilities, you may be able to improve them acoustically by using Tecnocell or the round Inno dampers, depending on the shape of the ventilation duct.