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Boat Engine Compartment Insulation Guide
Author: Eric Zuck
Last Updated: February 9, 2024
Read Time: 10 Minutes
Boat Engine Compartment Insulation Guide
Author:
Eric Zuck
Last Updated:
February 9, 2024
Read Time:
10 Minutes
Author: Eric Zuck
Updated: Feb. 9, 2024
Read Time: 10 Minutes
The engine is the number one cause of noise on a boat and is made worse with the addition of wind noise and vibrational noise from water hitting the hull. All of these noises add up to make it difficult to have a conversation with your friends and family, or even to just relax.
While the latter two are more "part of the experience", soundproofing and insulating the engine bay compartment is easy, and it's a great way to turn the noise down so you can truly enjoy your boat the way it was intended.
The engine is the number one cause of noise on a boat and is made worse with the addition of wind noise and vibrational noise from water hitting the hull. All of these noises add up to make it difficult to have a conversation with your friends and family, or even to just relax.
While the latter two are more "part of the experience", soundproofing and insulating the engine bay compartment is easy, and it's a great way to turn the noise down so you can truly enjoy your boat the way it was intended.
Popular Boat Soundproofing Materials
Learn how Adam got a 10 dB reduction By using Second Skin in his Boat engine Compartment
Second Skin Case Study: Boat Soundproofing
Before
Prepped
Damplifier Pro™
Heat Wave Pro™
"It's much quieter than before at idle/sunset cruise speeds making it easier to talk."
- Adam L.
Want great results like Adam?
The Benefit of Marine Engine Compartment Insulation
A 2017 study by Wakefield Research (according to BoatUS Magazine) found that 4 in 5 Americans say being around the water relaxes them. Scientists then found that even just looking at water “can trigger feelings of wellness, compassion, empathy, and happiness.” BoatUS Magazine seems like they may be pretty pro-boat, but we’ll take them at their word on this one.
An overly-noisy boat engine can unravel that relaxation in a hurry. A boat engine is typically only about 60-65 decibels when idling, but quickly ramps up to around 80 decibels of noise at cruising speeds and over 100 decibels at full-throttle for some boats. To put those noise levels in perspective, normal conversations can be heard with 70 decibels of background noise. At 85 decibels, you have to shout. And then at 100 decibels of background noise, you have to stand right next to each other AND shout to even have a chance.
Studies show that continuous exposure to more than 80 decibels of noise can cause nausea, fatigue, increased blood pressure, and insomnia. When you insulate your boat’s engine and create a more pleasant ride, you make it easier to do the very thing you bought the boat to do: relax.
This is me in my boat... someday.
Four Benefits of a Quieter Boat Engine
- More relaxing and more enjoyable rides
- Healthier rides due to reduced noise pollution
- Safer rides due to less distraction/inability to hear other boats.
- More legal rides if you need to comply with your state’s boating noise laws
When you’re out boating with the family and friends on your local lake or on the open water, why would you willingly subject yourself to those noisy conditions if you don’t have to? Let’s just nip in the bud right now so we can all relax and enjoy ourselves.
Choosing the Right Materials for Soundproofing and Insulating your Boat
Boats put out a lot of noise that can be hard to manage without the proper soundproofing materials and information. It's broken down to airborne noise and structural noise.
- Learn About Airborne Noise
- Learn About Structural Noise
- Most boat-related noises are airborne noises.
- The engine compartment needs to be as airtight as possible. Sound behaves like water. If you can look at your engine compartment, and see clear openings - those must be addressed first. If you don't... you basically have a hole in your boat, and decided to invest in a fancy water pump to remove the water instead of plugging the hole. A well-designed engine compartment should cut the sound you hear from an engine putting out 100 dBs to 70-80 dBs.
- Add sound insulation material to the hard-surfaces of the compartment. Hard surfaces reflect sound waves. By absorbing echos, there's less sound pressure inside your engine compartment AND less sound escaping the walls. By adding sound absorbing and soundproofing materials to all the hard, reflecting surfaces in your compartment, you can cut the noise level by 6-10 dBs.
- While often secondary to airborne noise issues, boat structural noise can be a big deal.
- A vibrational sound deadener is most impactful if you have a smaller doghouse. Adding it to the underside of the engine compartment is an added bonus. By adding sound deadener to 100% of the compartment, you'll increase the density of the compartment as a barrier while also damping structural vibrations.
- Our testing shows using a vibration damper is most impactful if you have a smaller doghouse, because the tighter compartment construction tends to transmit more structural vibrations.
- For a larger engine compartment where you have more airspace and the engine is mounted, the vibration damping material will be most effective close to where the engine is mounted, although we often see people add damping material to the underside of the lid.
Choosing the right sound deadener
The best sound deadening product for a boat engine compartment is Damplifier Pro™ Sound Deadening Mats. Most boat owners go with Damplifier Pro™ for it's ease of use — just peel and stick. We recommend 100% coverage as an added layer of thermal protection. Make sure to seal the edges with foil tape to protect the material.
Applying Damplifier Pro™ will stop the compartment from rattling and transmitting structural noise, while modestly increasing the amount of noise blocked (more noticeable for lighter compartments).
Alternative: Spectrum™ Liquid Deadener
Spectrum™ Liquid Deadener is a popular choice for metal boat engine rooms and any part of the boat experiencing heavy vibrations (like around a generator). Spectrum™ is a high heat viscoelastic polymer that sticks extremely well to a cleaned metal surface, and is easily applied with a spray gun, brush, or roller for a seamless, waterproof and rust-proof finish.
If you have a fiberglass surface, a self-etching primer is needed for Spectrum™ to "bite" in. We would recommend Damplifier Pro™ instead.
Choosing the right Insulation
Picking an insulation for your boat doesn't need to be complicated. We've done the research so you can enjoy the results! Both of our insulation choices have a foil backing, making it great for radiant heat AND great at absorbing the lower frequencies that engines give off!
Mega Block™ Hydrophobic Foam Heat Shield
If your engine compartment is mostly flat surfaces, Mega Block™ Hydrophobic Heat Shield is our go-to boat engine insulation! It's an open cell hydrophobic melamine foam covered by a 1000°F heat shield, which allows you to install it with only a 2" air gap from the engine. We've combine Damplifier Pro™ and Mega Block™ together in our Boat Insulation Kits.
Our peel and stick Mega Zorbe™ Hydrophobic Melamine Foam is our top-of-the-line, aerospace grade, sound absorber and heat insulator (just without the heat shield). This is a great way to add some absorption at the higher frequencies for larger engine compartments. Just be sure to leave at least a 6" gap between this and the heat source.
Heat Wave Pro™ Jute Insulation
If your engine compartment is mostly curved surfaces, Heat Wave Pro™ is extremely flexible sound insulation and automotive heat insulation that can fit those contours. These all natural fibers (no itch) are treated to be water resistant (no mold or mildew) and durable. Two things to note about Heat Wave Pro™ is that it should be installed at least two inches away from the heat source and its edges should always be taped with foil insulation tape in marine applications. Heat Wave Pro™ and Damplifier Pro™ can be paired together in our Boat Insulation Kits, as well.
Keep your boat's engine noise below deck!
How to Soundproof and Insulate a Boat Engine Compartment
We're just about ready to give you the ultimate soundproof and insulated boat engine compartment one can get. Are you ready?
Steps to Soundproof & Insulate a Boat Engine Compartment
-
- Clean the Surface - Remove any old insulation to expose the metal (or fiberglass). Then, use denatured alcohol to clean off any rust or dirt.
- Add Sound Deadener - Completely cover the boat engine compartment with Damplifier Pro™.
- Add the Insulation - Your second layer is Heat Wave Pro™ or Mega Block™, to add insulation and sound absorption. Mega Block™ for the straighter surfaces and Heat Wave Pro™ for the curved surfaces.
- Seal the Seams - Tape any seams with foil tape to protect edges and seams.
- Get out on the Water - Get that boat back out on the water! That's the smile of a man with a quiet boat!! :)
Boat... Meet Insulation. Insulation... This is Boat. You're Gonna Be Friends.
Your boat and this insulation are going to be best friends... they just don't know it yet. Get ready to introduce them. And introduce yourself to the peace of mind that comes from knowing you'll have the quietest boat at the dock.
- Damplifier Pro™ ends that vibrational noise from the fiberglass housing.
- Insulation and sound absorption for noticeable noise reduction and heat control:
- Mega Block™ for the straight surfaces
- Heat Wave Pro™ for the curves
Closing Thoughts
Insulating your boat’s engine compartment is relatively simple and should take you no more than a few hours. No matter what materials you choose, remember to leave adequate ventilation and be careful not to cover any exhaust vents. As you know, on a boat, water gets everywhere.
The good news is you have options depending on your type of boat and your goals. Let us know if we can help you figure out the combination that works best for you, whether it’s thermal insulation or noise blocking.. And when you’ve completed your project, send us pics and helpful tips so we can continue improving our guides and get your boat featured on our boat soundproofing customer projects page!
If you have any other problems with automotive or home soundproofing, check out our many other recommended posts! We have advice on how to reduce air conditioning noise, soundproof a room or office, and many more!