How to Soundproof a Boat Engine – The Ultimate Guide

I was never a big fan of boat rides, but about a month ago, my friends invited my family and me to go out on a boat to cruise and chill.

My wife was very excited, and was enjoying every moment of the trip. I was having a lot of fun at first, but the noise from the boat’s engine eventually became unbearable, and I could no longer have a good time.

The disturbing engine noise is definitely one of the main downsides of owning a boat. While on the trip, I made a few suggestions to the boat’s owner in regard to reducing the sound that was coming from the engine.

In this guide, I’ll share these same tips and tricks with you. In all honesty, it’s impossible to completely eliminate all the noise coming from a boat’s engine. However, if you follow these steps carefully, you’ll be able to reduce it to a manageable level.

How to Soundproof a Boat Engine

1. Soundproof the Outboard Motors

First, you’ll start by soundproofing the outboard motor, and then move on to the inboard motors.

Install Insulation in the Cowling

As you may have noticed, most boat engines are covered. The cover is called the cowling and is usually made of thin fiberglass. The cowling is actually a part of the engine, so it should be treated with care. One wrong move from you could cause it to malfunction down the line.

You can reduce your boat’s engine noise by insulating the cowling. For this, you’ll need to purchase some closed-cell polyurethane with aluminum backing to properly protect the foam from heat, grease and fuel.

The product I highly recommend using is the Uxcell insulation mat.

This will work extremely well, but although the foam is highly effective, it’ll only go as far as eliminating high-frequency sounds. If your main goal is to eliminate both high and low-frequency sounds, then you’ll need to use a dense and flexible material like Mass Loaded Vinyl.

MLV is flexible and thin, which makes it applicable in nearly any location you can imagine. The only downside I’ve found so far is the price, and this is why I specifically recommend the Stinger sound-dampening material.

When installing the material, make sure you cover as much of the inner cowling as you can, without obstructing any air vents or letting it touch any of the parts that move.

Obstructing the air vents can lead to the engine’s overheating. Furthermore, if the engine’s moving parts are obstructed, this can even cause engine failure to occur, although this rarely happens.

Insulate the Outer Part of the Cowling

If you don’t care how your engine looks, consider covering the outer surface of the cowling with insulation as well.

To insulate the outer surface, you’ll need a premade cowling cover, which you can typically find online. These covers are custom-designed; they should be very easy to use and it won’t cover any air vents.

Make sure you pay close attention when slipping one of these on. If you put one on incorrectly, this can cause overheating to occur.

2. Soundproof the Inboard Motors

Insulating the inboard motors will be a bit easier, as they’re already enclosed.

Get Some Rubber Insulation Matting

The first thing you’ll need to do is purchase some rubber matting, and I highly recommend this type.

It’s important that you don’t buy too much or too little. You can simply measure the area you need to cover and base your purchase on the measurements. Afterward, you can simply fit it under your engine.

Installing insulation matting will help decrease the amount of vibration between the motor and the boat.

Install the Insulation

You can now line the inside of the enclosed motor by using sound-deadening materials such as Mass Loaded Vinyl (check out the current price online). You’ll experience the best soundproofing results by using insulation panels that contain self-adhesive, as this will make the installation process a lot easier.

If you can’t find any of these panels, then it’s best to use green glue to stick the panels firmly to the motor. Make sure that you cover all the exposed areas, as even the smallest gaps will decrease the overall effectiveness of the insulation. I also suggest using mylar tape to cover all the corners and edges.

3. Cover all Gaps and Cracks

You should check and see if there are any gaps between the sheets of insulating material, and cover them with aluminum foil tape. You can also use this tape to cover any small gaps or cracks in the cowling and the engine compartment as well.

By covering all gaps, you’ll block all unnecessary areas through which sound may be able to escape. For the best results possible, I also advise using a few layers of tape on each gap.

4. Add Thickness to the Floor

I don’t recommend doing this for every boat—it all depends on the design. If the boat’s cabin or starboard is located above the inboard motor, then it would be a great idea to cover the floor with a sound-deadening mat.

I would personally go with this Rubber-Cal Shark Tooth Heavy Duty Mat. It may not look very appealing, but you can always cover it with something a bit more attractive, like a colorful rug to match your fancy cabin.

What Causes Boat Engine Noise?

Combustion engines always produce a lot of noise, because these engines are known for controlling explosions. Such noise is created by the vibration of the exhaust, as well as the propeller in the water.

Conclusion

If you follow the steps above carefully, you should have a quieter boat engine in no time. Before starting, though, keep in mind that these methods won’t eliminate the engine’s noise completely, although they will dramatically reduce it.

If you have any questions, please let us know by leaving a comment down below. For more information on soundproofing various objects and areas, you may want to check out our article about the best sound-deadening materials.

image: Pixabay