Boat Engine Compartment Insulation

Boat Engine Compartment Insulation Guide

Boat Engine Compartment Insulation Guide

If you’re fed up with the excessive noise on your boat, consider insulating the engine compartment. A boat’s engine is the number one cause of noise, and as you know, there is no shortage of noise while boating (#2: wind noise and #3: vibrational noise from water hitting the hull). All of these noises add up to make it harder to have a conversation with your friends and family, or even just to relax. Take a bite out of the biggest culprit of boat noise by soundproofing that loud engine and you’ll be much happier every time you take your boat out.

Even if your primary reason for insulating your boat’s engine compartment is to create a more pleasant boating experience, you should know that loud noise can turn into a health and safety issue also. Prolonged exposure to the level of noise that comes from boat engines can have serious consequences. We’ll get into it, but that’s why it pays to insulate your boat’s engine compartment — it’s safer and more enjoyable for all.

If you’re fed up with the excessive noise on your boat, consider insulating the engine compartment. A boat’s engine is the number one cause of noise, and as you know, there is no shortage of noise while boating (#2: wind noise and #3: vibrational noise from water hitting the hull). All of these noises add up to make it harder to have a conversation with your friends and family, or even just to relax. Take a bite out of the biggest culprit of boat noise by soundproofing that loud engine and you’ll be much happier every time you take your boat out.

Even if your primary reason for insulating your boat’s engine compartment is to create a more pleasant boating experience, you should know that loud noise can turn into a health and safety issue also. Prolonged exposure to the level of noise that comes from boat engines can have serious consequences. We’ll get into it, but that’s why it pays to insulate your boat’s engine compartment — it’s safer and more enjoyable for all.

Benefit of Marine Engine Compartment Insulation

When you insulate your boat’s engine and create a more pleasant ride, you make it easier to do something that most Americans agree is relaxing: spending quality time by the water. In fact, 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.

How does that relaxation get interrupted? With an overly-noisy boat engine. 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 at full-throttle for some boats. Studies show that continuous exposure to 90 decibels of noise can cause:

  • Nausea
  • Fatigue
  • Increased blood pressure
  • Insomnia
yacht on open water

What we all think our boat looks like

In fact, the Occupational Safety and Health Administration (OSHA) has set 90 decibels as the highest level a worker can be exposed to in your typical 8 hour work day. Every time the noise level is increased by 5 decibels, that hour limit is cut in half. So at 95 decibels, it’s 4 hours and then at 100 decibels, it’s down to 2 hours.

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.

Four Benefits of a Quieter Boat Engine

  1. More relaxing and more enjoyable rides
  2. Healthier rides due to reduced noise pollution
  3. Safer rides due to less distraction/inability to hear other boats.
  4. 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.

boat engine below deck with brown wood finish

Keep your boat's engine noise below deck!

How to Soundproof and Add Boat Engine Compartment Insulation

Boat engines put out a lot of noise, over 100 decibels at a wide-open throttle for some vessels. If you’re ready to reduce that noise and insulate your engine compartment, here’s what to do.

  1. Prep the area. You’ll need to clean the surface of your engine compartment and remove any adhesive that may already be there.
  2. Apply a primer to any fiberglass. Since most boat bodies and hatches are fiberglass (or some form of plastic), you’ll need to prime it before adding our sound deadener. We recommend POR-15.
  3. Apply sound deadener to metal underside of engine compartment. We recommend Spectrum, which can either be sprayed or painted on for a seamless, rust-proof finish. Spectrum is a high heat viscoelastic polymer temperature rated up to 400°F, which makes it ideal for the engine compartment. Applying Spectrum will stop the compartment itself from rattling and creating vibrational noise. If you’d like to use a sound deadening mat instead, you can use Damplifier Pro if you don’t expect the area to be regularly exposed to water. We recommend taping the edges to help ward off water leakage.
Damplifier Pro installed in boat engine compartment

Boat doghouse interior covered completely by Damplifier Pro

Tape the edges of Damplifier Pro - boat engine compartment

Tape the seams with HVAC tape to help protect edges

Heat Wave Pro inside the boat doghouse

Heat Wave Pro adds insulation and sound absorption. It's very flexible for curved surfaces.

  1. Install an insulator and heat shield. This is where preference comes into play. If you’re mostly dealing with curved surfaces, Heat Wave Pro will add the thermal insulation you need while acting as a heat shield. Heat Wave Pro is a high r-value (great heat insulator) sound absorber that is incredibly lightweight. 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. Although it’s mildew and mold resistant, taping the edges ensures a longer lifespan. For a more premium solution that is best suited for the mostly-flat surfaces in the engine compartments of larger boats, consider Mega Block. Mega Block is an easy peel-and-stick hydrophobic melamine foam that’s our top-of-the-line sound absorber and heat insulator covered with a heat shield. As with Heat Wave Pro, we recommend taping the edges and you should have a 2" air gap.
boat engine compartment

5. Block out noise with a sound barrier. If you’re dealing with a bigger boat and you’re determined to get as silent an engine as possible, creating a noise barrier on the outside of the engine compartment will make a huge difference. You can do this with one of our mass loaded vinyl products, Mass loaded vinyl has a high STC rating, making it an excellent sound blocking material. It’s heavy though, so it should not be installed on the inside of the engine compartment hanging upside down. On the outside, it’s perfect.

Spray or brush on a rustproof liquid deadener that dries with a seamless finish

Very flexible, insulating heat shield that will reduce noise and heat transfer. Treated for mold and mildew resistance

Our best combination of sound absorption and heat insulation. And it's hydrophobic!

Need Help with Your Boat Insulation Project?

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!