How to Soundproof an outboard motor?

In this blog, I’ll provide you with some soundproofing suggestions for an outboard engine. In all honesty, eliminating all noise from a boat’s motor is impossible. However, if you carefully follow these steps, you’ll be able to bring it down to a reasonable level.

Deep fishing, aqua sports like paragliding or water skiing, relaxing with a glass of wine while listening to the beautiful lull of the ocean, and so much more are just a few of the advantages of boating. However, as any boating enthusiast knows, there is one disadvantage to boating: noise. The boat motor is deafeningly loud, rattling the foundations of your being.

Getting out on the water on the weekends is a very soothing activity unless you have a noisy motor. If that’s the case, it’s a constant assault on your ears, and because sound travels farther through water, it’s also an assault on the ears of anyone unfortunate enough to be close to you.

Although most engines have a covering, it usually does nothing to mask the excessive noise. The cowling is the term for this style of covering. However, unless you complement or top it up with something significantly greater, it is ineffective and inefficient.

Outboard motor noise is undoubtedly one of the disadvantages of owning a boat, but I can assist you with a method for soundproofing an outboard motor on a budget.

This tutorial seeks to provide some advice on how to lessen the noise produced by your engine. But, let’s be honest, you’ll never be able to entirely eradicate all outboard motor noise; it’s simply impossible.

However, by following the advice in this blog, you may bring it down to a manageable level.

How to Soundproof an outboard motor?

I’ll give you a step-by-step guide on how to lessen the sound of your outboard engine below. Then we’ll go over how to do it in detail, hopefully without spending a fortune.

  • Install Insulation in the Cowling
  • Insulate the Outer Part of the Cowling
  • Double-check to see if you need more soundproofing
  • Consider Changing engine

Why should you soundproof an outboard motor?

Let’s start with the most important reason for soundproofing your outboard motor. The noise generated by your boat overshadows the benefits of boating, which include relieving stress, anxiety, and other minor ailments by giving a therapeutic cure in addition to pure sea air. Furthermore, boating enhances your brains because you must think quickly and memorise nautical phrases when steering your ship.

Furthermore, boating is a social enterprise that allows you to interact with a wide range of people, including family members. Unfortunately, all of these advantages are lost if your boat’s motor is simply too noisy. Here’s how these loud noises and vibrating vibrations might impair your health and well-being:

  • The motor on a boat can reach decibel levels of over 110. This is a frightening level that carries significant risk. Hearing loss is something that can happen to you over time.
  • Vibrations of extreme intensity have the potential to degrade your bones and muscle tissues, resulting in major health problems. Though this is not a typical occurrence, it is still a possibility, therefore you must take the appropriate precautions to avoid falling into such a terrifying situation.
  • When the speed of your outboard motor is too high, you run the risk of being injured. They have a directly proportional relationship. When the engine is this loud, there is a great danger of misinterpretation among the passengers. Because you can’t hear your friends’ warnings, you’re more likely to make a bad mistake, steer in the wrong way, and so on.

As you can see, soundproofing your outboard motor is important. It not only makes it difficult to converse with your passengers on board, but it also has major health implications that could injure you. As a responsible boater, you must never put yourself or your passengers in danger, which is why soundproofing your engine is essential.

Install Insulation in the Cowling

Most outboard motors are covered, as you may have seen. The cowling is the name for the cover, which is usually made of thin fibreglass. Because the cowling is an integral part of the engine, it must be handled with care. You could cause it to break down in the future if you make one wrong action.

The cowling can be insulated to reduce engine noise on your yacht. You’ll need closed-cell polyurethane with aluminium backing for this, which will protect the foam from heat, grease, and fuel. The Uxcell insulation mat is a product that I strongly recommend.

This will work well, but the foam’s effectiveness will be limited to the elimination of high-frequency sounds. If you want to eliminate both high and low-frequency sounds, dense and flexible material like Mass Loaded Vinyl is the way to go.

MLV is flexible and thin, making it suitable for use in almost any environment. The only drawback I’ve discovered so far is the cost, which is why I recommend the Stinger sound-dampening material.

When attaching the material, make sure to cover as much of the inner cowling as possible without blocking any air vents or allowing it to come into contact with any moving parts.

The engine can overheat if the air vents are obstructed. Moreover, if the engine’s moving parts are clogged, this can result in engine failure, but this is uncommon.

Materials Needed
closed-cell polyurethane
Uxcell insulation mat
Mass Loaded Vinyl
Stinger sound-dampening material.

Insulate the Outer Part of the Cowling

You can even cover the exterior surface of the cowling if you don’t care about your engine is a little unattractive.

Purchasing a ready-made cowing cover is a good method to do this. This will be custom-made for your vehicle and will not hide any air vents. They also look nicer than anything you could scrounge up on a weekend.

Although they were not intended expressly for sound insulation, they have been observed to greatly reduce sound levels, which will aid in the overall process of making the outboard motor quieter. Make sure the sound-dampening materials are in place and that there are no obstacles.

The next step is to make sure the inner cowling fits the material as closely as possible. You must ensure that no air vents are blocked and that your additional padding does not come into contact with any moving parts. This can harm your boat’s engine.

Overheating might occur if the air ventilation system is obstructed. It will also compromise the motor’s integrity. Worse, this is a safety danger that could result in a serious accident.

The same is true if your soundproofing materials come into contact with any moving parts. Because friction is created by moving elements, any obstacle can result in a disastrous outcome. In the worst-case scenario, the engine may completely fail.

As you work on your soundproofing job, keep an eye on the air movement. To avoid a variety of problems, be careful in ensuring that there are no obstructions wherever.

Double-check to see if you need more soundproofing

If you believe that greater sound dampening is required, you may need to cover the surface area of the cowling itself. The first two methods will help to reduce noise, but the more effort you put in, the more the sound will be muffled.

Using a Mercury Motor Cover, for example, is a good idea because it can be modified to suit your outboard motor. Slippage should be avoided at all costs since it can cause your engine to work overload and overheat. If anything doesn’t appear quite right, make the appropriate changes.

Materials Needed
Mercury Motor Cover,

Build a noise-shielding enclosure

It’s as simple as putting a piece of plywood over the transom to deflect the engine noise away from the driver. Take measurements of the transom’s width and the engine’s height above it. Cut a piece of plywood to these measurements and mark out a space for the engine’s handle to pass through. Screw the plywood to the transom.

Consider Changing engine

If the above fails, Four-stroke outboards are quieter than two-stroke outboards. Engines from various manufacturers are associated with varying levels of noise. Suzuki and Evinrude both make extremely quiet outboard motors. However, keep in mind that a quieter engine may be less powerful.


While it may appear to be a major issue at first, a noisy outboard motor is a rather simple problem to resolve. You can solve the problem while also making the most of your boat by following these instructions.

If you carefully follow the procedures above, you should soon have a quieter outboard engine. Before you begin, take in mind that these techniques will not fully remove engine noise, but they will significantly reduce it.

Frequently Asked Questions (FAQs): How to Soundproof an outboard motor?

What can I do to make my boat motor quieter?

If you need to soundproof an inboard motor compartment, a high-quality soundproofing foam barrier can help you reduce noise by up to 35 decibels. To prevent sound from escaping through and ensure that panels fit securely together, use a soundproofing sealant or tape to seal panel seams.

Are two-stroke outboard motors noisy?

A 4-stroke engine is also much quieter, whereas a 2-stroke engine is much louder and produces a characteristic, high-pitched “buzzing” sound.

Is it true that having an engine cover reduces noise?

The covers minimise engine noise and protect the engine from dust, debris, and other contaminants while also giving the engine area a cleaner appearance. The “insulation” on the underside of a hood is a fire blanket, not noise insulation.

How can I soundproof my engine compartment?

Placing dampening or deadening mats with adhesive backings underneath your car’s bonnet is the best approach to sound deaden the engine. Simply measure the size and form of your car’s hood, cut the mat to fit, then gently place it under the hood.

What causes the vibrations in an outboard motor?

A damaged or compromised propeller is one of the most common reasons for outboard engine vibration. Throttling to higher RPMs accentuates the vibration, which is a hint that your propeller is the root of your problem.

When driving a boat, how do noise and vibration affect you?

Noise and vibration on a boat can be distracting, reduce your reaction times, and obscure your judgement, making it difficult to maintain good control of the vessel. Noise and vibration might make you feel fatigued by affecting your body.

On an outboard motor, where is the exhaust?

The bottom fin of the propeller is where the majority of an outboard’s exhaust is released. This is why when the boat is started, bubbles appear from the propellers. This exhaust is also combined with some cooling system water.

Is it louder to use two or four-strokes?

A 2-stroke engine typically produces more torque at higher RPMs, but a 4-stroke engine produces more torque at lower RPMs. A 4-stroke engine is also much quieter, whereas a 2-stroke engine is much louder and produces a characteristic, high-pitched “buzzing” sound. 2-stroke engines, on the other hand, are more powerful.