Sound insulation in order to make your boat, yacht or sloop quieter

Explanation About Insulating Boats and Yachts

Noise nuisance while driving a boat greatly limits your enjoyment. In this article, we will explain ways to improve your pleasure craft or vessel. The properties of the products that are mentioned can be found on the corresponding product pages.

Decrease engine noise

The propulsion of a boat is the main source of the nuisance. The engine noise is already being blocked to a certain extent by barriers such as the machine room or the housing, but often this is not sufficient. In order to really block the noise, (that is, to isolate) these barriers should be covered with the right acoustic insulation material as much as possible and be free from any sound leakage.

Mass = Insulation

When it comes to acoustic insulation, the optimal way is to add mass by means of a base layer (thin, but heavy acoustic insulation material) with a layer of absorption material on top of it (in order to mute sounds and airborne noise). A qualitatively insulated housing is made of a solid construction from sturdy material and closes off well without any sound leakage (!). In order for a housing to function well, the in- or outside should be equipped with Isomat TS8 or Isomat TS14. This increases the weight by 8 or 14 kg per m2, it is irrelevant at which side this weight is added. The heavier the housing, the higher the insulation value, the better the end result. Do you already have a housing around your engine that consists of steel plates thicker than 4 mm? In that case you should increase the mass and stiffness by means of Vibradamp anti-drumming paste and Zincor steel plates. After the pasta has completely hardened you can cover the whole thing with absorption material. Are you planning to build a housing yourself? In that case Merfoplex is a suitable choice when it comes to the manufacturer’s plate. This plate contains a core of Isomat which gives it excellent acoustic insulation properties.

Absorption = Muting

The inside of the housing should be covered with absorption material in order to mute the engine noise. We developed a few products for various situations: outboard engine, little space, and high temperatures; big ships with heavy or low noise from a diesel engine; yachts and vessels with large machine rooms. In spaces with high temperatures and where the absorption material is very close to the hot parts of the engine or exhaust, we recommend you to use Aluglass 15S. This mainly applies to outboard engines or small engine housings. In these cases, the exhaust should be wrapped with Glassfiberband, since this decreases the risk of fire during maintenance of your boat. Apart from that, this layer protects the applied absorption material. Inside a housing where the distance between the parts of the engine and the absorption material is only 10 to 15 cm you should use a product that contains a GW top layer.

Different absorption products with different properties

  • Acusticab: flexible absorption foam with an oil- and heat-resistant PU top layer*. Generally applicable, resists temperatures up to 70 °C, self-adhesive. Black and white. Decoratively compressed top layer. Various thicknesses.
  • Flamex GW: Sturdy absorption foam with a GF top layer*. Can only be applied to even walls. Resists continues temperatures up to 150 °
  • Flamex PU: Sturdy absorption foam with a PU top layer. Can only be applied to even substrates. Resists continues temperatures up to 100 ° Self-adhesive. Black top layer, various thicknesses.
  • Merfocell GW: Flexible absorption foam with a GF top layer. Can also be applied to curved surfaces. Resists temperatures up to 100 °
  • Merfocom: Stiff composite plate with an insulation core of Isomat TS8 on a 3 mm foam decoupling layer, and a MerfoCell GW absorption plate of 25 mm. Resists temperatures up to 100 °C. Please note: Because of the weight of this product, it is advisable to use pin bonding fasteners in case you want to mount the product against the bottom of a floor, housing or shutter. The adhesive layer of self-adhesive products resists temperatures up to 70 °C. In case of doubt you can use the pin bonding fasteners with a Nelson cover. Is the distance between the absorption material and the hot engine parts more than 15 cm? Then use the following absorption materials (provided there is enough ventilation):
  • Merfocell PU: Flexible absorption foam with an oil- and moisture resistant PU top layer. Generally applicable, resists temperatures up to 70 ° Self-adhesive. Colour: black. Various thicknesses.

* Glass cloth fiber top layer.


Merfocell PU applied on a engine housing

Insulating the ship's hull

Another method of insulating that is not used very often is the ‘sandwich anti-drumming principle’, even though this is a very effective way to insulate. Apply this method on steel with thicknesses starting at 4 mm in order to insulate resonance and strongly reduce the radiation of noise, both in- and outside the vessel.

Anti-drumming = insulating

Contact noise is produced by plate surfaces that vibrate and thus create audible sound. Vibration in the ship hull coming from the engine, propeller, bow thruster and appliances such as a generator are converted into sound, causing nuisance throughout the vessel. This vibration travels through the walls and floor of the relatively light ship hull. Vibradamp anti-drumming paste with Zincor steel plates pressed into it insulates the vibration directly at its source. The vibration is being neutralized, because the treated surface is being ‘held’, in the same way as when you would hold a gong in order to mute it. Vibradamp ‘sandwich anti-drumming’ material should be applied in an area of about a meter around the source of the noise. The more you use, the better the result will be. Areas of application: mirrors, swimming platform, bottom and ship hull, walls, floors and the hull around the bow thruster. Insulating a polyester ship hull, walls and shutters can also be carried out using Isomat TS8 or TS14.

Insulating floor, deck or shutter

A floor, deck or shutter above the engine often becomes a source of nuisance, because of the stiff way in which it is mounted and its light weight. Decouple the floor by mounting Regufoam Strips between the thwarts and the floor, preventing contact noise. After that the floor should be equipped with the Isomat TS14 and KE14J mass plates, which makes the floor 14 kg per m2 heavier and noticeably increases the insulation value.


Please feel free to contact us, we will be happy to answer your question as soon as possible. The Boats & Yachts page contains additional solutions with regards to shipping.