Boat Engine Soundproofing: How to Reduce Noise & Vibrations

In all honesty, I never quite understood the appeal of boats and cruising in them until I was a fair bit into adulthood. It just seemed like a pointless risk to me, the sort of thing you do when you feel like getting the same enjoyment out of lying at the beach is too ordinary for you.

My mind has been changed, though not entirely, by relatively recent events. My family and I were invited to go on a friend’s boat, out into the water to cruise and have fun.

My husband was loving every moment, acting like he was going to buy about 4 different boats as soon as we got back. My kids loved it even more, somehow, taking photos and just having a blast.

Then the noise became noticeable. An ungodly, core-shaking level of loudness that nearly ruined it for me.

I kept thinking about suggesting various solutions and ways to mitigate this to the boat’s owner. Let’s go into them now.

soundproof boat engine

All About Boat Engine Soundproofing

Let’s go over some essentials in regards to the reasons why you should soundproof your engine compartment and the benefits. Next, we’ll explore how to do it in detail and ideally not pay out the nose for it.

Why should you soundproof your boat engine

  • The therapeutic and health benefits versus the issues that may arise
  • The social benefits versus the social negatives

Let's take a look at both of these. While they may seem obvious, there are a thousand little details that can be forgotten, when discussing this topic.

First of all, let me list some examples of negative consequences to your health if your boat's engine is too loud and vibrates it too much:

  • Hearing damage over time. As boats can easily create noise above 110 decibels, this is a very real and very terrifying risk.
  • Degradation of your bone and muscle structure. Vibrations, at a high enough intensity, are quite capable of causing these types of physical ailments in some people.
  • While not common, they’re still a possible danger and betting that you’ll be one of the lucky ones is never advisable.
  • Exclamation Circle
    Risk of injury. From miscommunication to slipping up, the ways to injure yourself in these kinds of situations are far too numerous to count.

Now let’s look at the positive aspect. Boating, after all, can be very beneficial to your health.

boat engine soundproofing

It reduces stress, anxiety, acts therapeutically towards any mild ailments due to the fresh sea air and even helps keep your wits sharp. After all, remembering all those nautical terms, how to steer a boat and so on do help to keep you on your toes, mentally speaking.

How to soundproof your boat engine

Let’s see how you can reduce the noise of your boat to a level you can cope with, so you can fully enjoy and embrace all the benefits of it.

Be aware that there is no such thing as eliminating the noise fully. Regardless, you can reduce both that and the rumbling to very tolerable levels, making it moot.

There are generally 2 major steps to dealing with the noise:

1. Soundproofing the outboard motors

While most engines have a cover over this type of engine, it usually does very little to mitigate noise. This cover, called the cowling, is largely ineffective unless you supplement it with something far better.

Keep in mind that your cowling is a piece of the engine that you need to tread lightly with. Generally speaking, it’s not that delicate, but some wrong moves can cause issues down the line.

Depending on the material used to make it, it may be more or less prone to malfunctioning, if tampered with, as well as sturdier or more brittle. Make sure to thoroughly consult your manual, first.

Let’s see how you can reduce the noise by installing insulation into the cowling and, optionally, on the insulation as well. While this may seem redundant, with how loud the engine can get, it may not even be enough, despite you potentially soundproofing both.

  • Foam can be useful, but it only eliminates the high-frequency sounds. For best results, I recommend getting something like this, since it eliminates both ends of the spectrum, being dense flexible enough to do so.

Make sure to shop around and see what fits your needs best. If you have to, consider bringing in an expert, or at least someone with experience dealing with things like this, to aid you.

  • Fit the material, covering as much as you can of the inner cowling. Do not obstruct any air vents or let it touch on moving parts.

Obstructing the air vents can lead to overheating, among other things. At best, this erodes the integrity of the motor and at worst it can be an actual safety hazard, the type that may end up causing an accident.

Furthermore, moving parts can cause friction, if they are obstructed and the possibility for disaster there is endless. If that wasn’t enough, they can even cause total failure of the engine, in some rare cases.

outboard-boat-engine

Check if air can still flow regularly. Make sure to not be causing a block anywhere or there might be issues down the line.

  • Next, consider the effect you’ve gotten so far. If you think you need more soundproofing, go for a cover on the surface area of the cowling itself.

As a general bit of advice, try not to expect miracles from either the first or second step here. While what you just did will reduce the noisiness by far, it’s still reducing something that’s massive in the first place.

Products like these are generally your best bet. They're custom designed and should be easy to use while being better than any alternatives.

Be wary of slipping these on wrong, however, because the engine might overheat. If something does not look right to you, adjust it.

2. Soundproofing the inboard motors

  • These tend to be a lot easier to soundproof, due to being pre-insulated. Get some rubber insulation matting from the choices you can find online or at your nearest store.

Make sure not to buy too much or too little, since that’s a common mistake. Even if it may be tiresome, measuring the surface area you need to cover or using the manual, at least, as a reference, is best.

  • Line the insides of the enclosed motor with the matting. I recommend using the self-adhesive ones, for best results and ease of use.

Covering everything you possibly can is best, but be wary of covering too much. The possibility of overheating rears its head here as well if things go poorly.

inboard-boat-engine

Generally speaking, you don’t need to pay much attention here, but keep in mind that cracks in the insulation or lopsided application will provide worse results. Go slow and be patient for the best possible outcome.

One thing I recommend is taking your newly insulated motor on a test-run. Carefully maneuvering around the pier itself will give you a good notion of whether it worked or not.

Taking any risks with this is ill-advised and you should always tread with caution. For the best results, checking if everything works methodically will be your best bet.

Not to say you shouldn’t enjoy your newfound quieter cruising, just be understandably slow at first.

Conclusion: On Boat Engine Soundproofing

While it may seem like a big deal, once you first experience it, a noisy boat engine is very much an easy problem to fix. With these steps, you can take measures to both correct the problem and make the most of your boat.

That way, you’ll get all the benefits, without any of the downsides and you’ll only enjoy yourself all the more.