How To Soundproof Noise From Boat Engine – Inboard & Outboard Motor

Whether you enjoy spending time out at sea or spend your days on freshwater lakes and rivers, you know that boating is a great source or recreation and relaxation. Some of us use boats for fishing, while others prefer tubing and water skiing. But no matter where you do your boating or what you do while you’re out on the water, you have probably wished that the motors weren’t so loud.

How do you soundproof noise from a boat engine? It takes a lot of power to move a boat through the water at decent speeds. For most boats, that power comes from internal combustion engines. Whether your craft is powered by gasoline or diesel, there is a lot of noise that comes with running at high throttle. Fortunately, there are steps that you can take to reduce the amount of noise you’ll hear.

There are ways to get a completely silent day on the water—a kayak, a paddleboat, a canoe. But most of us want a little more range and speed with a little less work. That means that motors are a necessary part of the equation, and where there are motors, there is noise. You can’t completely eliminate the noise of an inboard or outboard motor, but you can reduce it. Read on to learn how!

What You Need to Know About Soundproofing Noise from a Boat Engine

The first thing that you need to know about soundproofing noise from a boat engine is that you need to have realistic expectations. Depending on the size of your boats motor and the location where it is mounted, people riding in the craft may be exposed to as many as 110 dB when running at full throttle. Soundproofing can absorb some of the noise, but it won’t eliminate it entirely.

Whether your craft has an inboard or outboard motor, the principle of soundproofing is the same. Your goal should be to create barriers with sound-absorbing material so that less of the noise is able to travel from the motor’s location to the areas of your boat where people are riding. The techniques for how to do this and the best materials to use will differ depending on the type of motor your boat has, but the principle remains the same.

Anything that you do to soundproof the engines of your boat has to be done in such a way that it doesn’t interfere with the motor’s functioning. If you install soundproofing improperly, it might lead to overheating that can cause engine damage or other problems that could lead to failures out on the water and expensive repairs.

Of course, all boats are different, and some are louder than others. If you’re fishing, you might run loud to get where you’re going and the anchor or drift. If you’re spending the day towing skiers, then you’ll likely be exposed to near-constant noise. If you’ve done all that you can to soundproof the boat and you find that the noise levels are still too high, you may need to provide passengers with earplugs or earmuffs to supplement the effects of the work you’ve done.

How To Soundproof An Outboard Motor

How To Soundproof An Outboard Motor

Since outboard motors are mounted on the exterior of the boat’s hull, there is little that stands between the noisy powerhead of the engine and the people riding in the boat. In most cases, there is just a thin fiberglass shroud over the powerhead that is called a cowling. By itself, the cowling doesn’t do much to absorb and dampen the noise of the engine, but it gives you something to build upon.

Most people who want to reduce the engine noise of their outboard motors choose to add soundproofing to the inside of the cowling. Some people will add additional material to the outside of the cowling, while others prefer not to for aesthetic reasons. It all comes down to what seems like the right balance of comfort and style for you and the people you’ll be boating with.

If you choose the right materials, you may be able to get all of the soundproofing you desire from what an internal application can provide. Polyurethane with aluminum backing is inexpensive and heat resistant, but it tends to be most effective on high-frequency noise. Mass Loaded Vinyl is another material that can be applied to the inside of the cowling. It works for high- and low-frequency noise, but it is more expensive. 

Either way, you choose to go with internal soundproofing, you’ll need to leave gaps for the air vents in the cowling and make sure to avoid contact with moving engine parts. If you wish to increase the amount of sound absorption and you don’t mind sacrificing the sleek look of the fiberglass cowling, you can add additional sound insulation to the exterior. There are many manufacturers who offer custom fitted solutions that will supplement the noise absorption of your internal soundproofing.

How To Soundproof An Inboard Motor

How To Soundproof An Inboard Motor

Soundproofing an inboard motor is typically easier to do, and you can expect better results from the process. Since the motor is already enclosed in a compartment, you can work with the interior surfaces of that compartment. Once you’ve applied the sound insulation to the interior walls of the engine compartment, you can follow up with tape, foam, or both to seal any gaps that might let sound leak through.

The more surfaces that you cover with sound-absorbing material, the greater the overall reduction in noise for you and your passengers will be. If you are having the motor pulled for maintenance or repairs, that is a great opportunity to do a sound insulation project while you have unobstructed access to the compartment. If you don’t anticipate an opportunity like that in the near future, you’ll have to do the best you can to piece sound insulation into obstructed areas.

You can try to get the project done with aluminum backed polyurethane if you’re on a tight budget, but if possible, it’s well worth the extra expense to go with Mass Loaded Vinyl. Not only will you have an easier time working with self-adhering panels of Mass Loaded Vinyl, but you’ll get effective sound dampening across the full spectrum of frequencies. It’s best to work with the largest pieces possible to reduce the number of gaps that you have to seal later on.

Once you’ve applied all of the soundproofing material to the engine compartment, you’ll want to seal up all of the gaps in the material with tape or foam. That will give you the most complete barrier to engine noise between the interior of the compartment and the passenger area of the boat. Of course, you’ll need to make sure that your installation doesn’t obstruct any vents or get in the way of moving engine parts.


If you’re looking for a peaceful day on the water, there are always going to be trade-offs. You can have a boat that is nearly silent, but to get it you’ll have to rely on the wind in the sails or paddles in the water. If you want the speed and power to cover distances and tow skiers, then you’ll need a noisy internal combustion engine. But if you invest the time and effort to complete a sound insulation project on your boat, you can get the best of the speed and power while reducing the downsides of noise as much as possible. 

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