# Best way to soundproof engine compartment?



## FrankLanger (Dec 27, 2005)

The soundproofing in the engine compartment of my 30 foot sailboat (inboard engine) consists of foam with a silver foil covering. It is crumbling badly and needs replacement.

I am thinking that I need to use a broad putty knife, and maybe eventually sandpaper to get rid of the old stuff, and then install new soundproofing material. But I would welcome any advice on how to do this properly--both removal and installation of the new stuff. As well, if there are different kinds of insulation material, any recommendations on what to watch for would be welcome.

Thanks,
Frank.


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## bestfriend (Sep 26, 2006)

"Here here" I am in line for that too. I can't here myself think.


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## sailingdog (Mar 19, 2006)

Most auto parts stores will sell sound proofing material suitable for use in an engine compartment. 

Your idea for removing it sounds fine... may need to use a solvent of some sort to clean off any adhesive residue from the old stuff as a final step.


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## FrankLanger (Dec 27, 2005)

I have seen advertising from SailorSolutions which promotes what they call an especially effective (in reducing noise) product, that comes in one foot square tiles with sticky adhesive, and a hard/washable top plastic-like cover. Costs about $10/tile, and they suggest I would need about 20 of these. Has anyone used these, or something similar?
Are there different grades/qualities of material for engine soundproofing, and if so, is the difference sufficiently noticeable to justify any price differences?
Thanks for the responses so far, and welcome any others.
Frank.


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## sailingdog (Mar 19, 2006)

If they're plastic...they're probably not too suitable for the engine compartment. Sound proofing materials for the engine compartment generally have to withstand fairly high temperatures... depending on how close to the engine the material will be, and as such most are not plastic.


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## FrankLanger (Dec 27, 2005)

Yes, that makes sense, so I'll have to check if they are heat-resistant or not. I have images in my mind of me stuck in the engine compartment with rolls of very unwieldy soundproofing material all over the cabin sole, and trying to measure, cut straight sections, hold it in place, having it fall down again, etc. Is there an easier way to do this?
Frank.


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## sailingdog (Mar 19, 2006)

FrankLanger said:


> Yes, that makes sense, so I'll have to check if they are heat-resistant or not. I have images in my mind of me stuck in the engine compartment with rolls of very unwieldy soundproofing material all over the cabin sole, and trying to measure, cut straight sections, hold it in place, having it fall down again, etc. Is there an easier way to do this?
> Frank.


Yup... pay someone to do it for you...it's easier in every way except on the wallet.


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## hellosailor (Apr 11, 2006)

The best stuff for boat engine compartments will, sadly, be marine grade. There are a couple of products that look like foam rubber with a layer of lead or dense vinyl and a mylar face (over the foam) to keep oil out of it. Sold in rolls or tiles to be cut and glued up, or self-stick, like what you're scraping off.

The problem with the stuff in the auto/home stores is that the foam may not stand up to the moisture and heat in an engine compartment--and it should be flame resistant, too. Then there's quality...even JCWhitney used to sell this stuff but their quality has been known to vary.

The lead/vinyl absorbs energy just because it is so dense. The foam decouples that vibration from the engine compartment walls, and in theory you get less noise. There are usually special mounts/ties that will also let you hang the stuff so that they take some of the weight (from the dense layer) and still decouple some of the noise. This is one of those jobs where there's enough labor that it is worth doing the job "right" with better materials the first time.

There are also some sound absorbing coatings that are sold, kinda like a gallon of heavy silicon rubber, that are supposed to work well--but they're designed more to keep thin metal/frp panels from vibrating and resonating, the thick foam+lead stuff still is unmatched.

"Acoustic controls" and "soundproofing" suppliers on the web usually turn this stuff up, but the good stuff is never cheap.


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## Faster (Sep 13, 2005)

Marine chandleries also carry a foam based product, with a thin lead-like layer and backed with silver foil about 1" thick. It can be glued in with the foil showing, making for an easy-to-clean surface. We replaced the worn out lining on our boat with this stuff, about $75 for a 36x48 piece. Not cheap but it works and looks good. We have glued it in with 3M spray contact cement and it has held fine in the engine box temperatures.

One side of our engine area isn't walled off from the galley sink, so we hung a curtain along the engine made from the same material.

On our last boat we had great sound dampening using an old dentist's X-ray apron, draped over the engine. This was very effective in addition to the soundproofing of the engine box itself.

Another option available is a lead-layered rubber curtain that is used in Industry to surround noisy machinery like air compressors. About 1/8- 3/16" thick, it has pretty good soundproofing properties but is quite heavy. It too can be glued in or hung like a curtain.


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## arshid112037 (Nov 12, 2013)

Hi
Respected sir 
we have designed an ambulance boat the dimensions are as under 
Length = 12m
Breadth= 3.6m 
Draft = 1m 
Max weight = 12tons
so there is a patient compartment which consist of 4Xpatients stretcher under the such compartment there is two engines 200KW each and one Diesel generator 100KW are exist and during the operations of such machinery the noise created should be transmitted to the patient compartment that is not suitable and comfortable to the patient so the recommended noise level in such compartment is 50-60dBplease suggest us the suitable and recommended SOUND PROOF INSULATION System that can be used for suh Boat 
Thanks


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## mitiempo (Sep 19, 2008)

You have resurrected a very old post but here is a link to the product I sell in Canada. I am not sure where you are located. The link is from Jamestown Distributors in the US. It is a high density fireproof foam in 2 layers with a mass loaded vinyl between them. It is covered with a foil surface and a which is easy to keep clean. It is sold with a mounting system and usually contact cement is used as well. It should be available where you are located. Hope this helps.

Soundown Composite Insulation Vinyl/Foam Sheets

Here is a link to a pdf showing the product details.

http://soundown.com/Section 2 PDFs/2.1 PDFs/Vinyl Foam.pdf


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## deltaten (Oct 10, 2012)

I lined the engine compartment hatch with 1" foil faced fiber-glass duct board. Creative use of *real* aluminum foil duct tape sealed the edges and reinforces the mastic which fastens it to the 1/4" ply.It works so well that I intend to apply it to the entire compartment....some day . The compartments bulkheads are plywood; so a few screws with fender washers to keep it in place till the mastic sets is all it will take. Then a contortionists game applying tape to the joints/seams.....
Avail. at most HVAC suppliers and possibly by order at big-box stores?

HTH


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## mitiempo (Sep 19, 2008)

Without the mass loaded high density layer the low frequencies of the diesels will not be reduced to a low enough db level.


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## MarkSF (Feb 21, 2011)

I used the Soundown stuff, 1" thick, except under the cockpit sole, where I doubled it to 2". Honestly, the main noise is now from the exhaust, when under way. I would seriously like to do something about that. I have been wondering if my 30 year old silencer box is losing some effectiveness.


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## Missingyou (Aug 16, 2013)

mitiempo said:


> You have resurrected a very old post but here is a link to the product I sell in Canada. I am not sure where you are located. The link is from Jamestown Distributors in the US. It is a high density fireproof foam in 2 layers with a mass loaded vinyl between them. It is covered with a foil surface and a which is easy to keep clean. It is sold with a mounting system and usually contact cement is used as well. It should be available where you are located. Hope this helps.
> 
> Soundown Composite Insulation Vinyl/Foam Sheets
> 
> ...


This is same stuff I have been considering for my generator cabinet. It's one of my winter projects. Unfortunately it's a bit on the expensive side, but it is the correct product to use.


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## hellosailor (Apr 11, 2006)

An ambulance boat is such a novel concept.

Can you tell us if this is all a custom build?

What the range and speed are, and the intended area of operation?


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## Deric (Feb 3, 2008)

What about neoprene ? It is supposed to be oil resistant, water resistant; it's the same material scuba diving suits are made.


One can purchase sheets: various sizes and thickness.


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## jimgo (Sep 12, 2011)

Deric, I think neoprene would be good for damping vibrations, but it doesn't have the mass to absorb and dissipate the sound energy.


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## Dave_E (Aug 7, 2013)

There are 2 kinds of marine engine compartment insulations. One is for gas, the other for diesel. I just re-did my doghouse... it's not that hard. Good sturdy putty knife took off the old stuff. Sanded down the old glue spots with big grit paper. Use spray glue in a can MADE FOR FOAM. Found a can at my local hardware store. The new insulation (as mentioned) is pricey. Don't skimp if you can, you'll be glad you didn't. Cuts with a good heavy pair of scissors (might have to borrow your neighbor's jocko kid though) 

Dave


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## hellosailor (Apr 11, 2006)

Neoprene foam is dense, but it is also expensive and flammable. And the less expensive "chemical blown" neoprenes tend to degrade faster in heat, i.e engine rooms. 

If it was the right material for the job you'd see it used on production boats.


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## mitiempo (Sep 19, 2008)

Dave_E said:


> There are 2 kinds of marine engine compartment insulations. One is for gas, the other for desiel. I just redid my doghouse... it's not that hard. Good sturdy putty knife took off the old stuff. Sanded down the old glue spots with big grit paper. Use spray glue in a can MADE FOR FOAM. Found a can at my local hardware store. The new insulation (as mentioned) is pricey. Don't skimp if you can, you'll be glad you didn't. Cuts with a good heavy pair of scissors (might have to borrow your neighbor's jocko kid though)
> 
> Dave


Spray glue is used in conjunction with a fastening system supplied with the foam. The glue by itself will not hold the weight long term.


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## jrd22 (Nov 14, 2000)

3M makes two "strengths" of foam spray adhesive, the stronger (90?) holds up the heavy 1.5" foam with the barrier in it for about a year and a half on the overhead sections (much longer on the vertical areas). This is in a powerboat that sees a lot of rough water. We bought our sound proofing stuff from Hamilton Marine here in WA, very similar to the stuff that Mitiempo sells in BC.


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## Dave_E (Aug 7, 2013)

The original foam insulation from 34 years is what I took off. It was glued on. If you find glue that can be brushed on for foam... Go for it. You don't need to coat the whole thing.


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## mitiempo (Sep 19, 2008)

If it is just foam it will last for years with only glue holding it on. Soundown is heavy because it has the mass vinyl layer in the middle - this is what quiets the deeper sound of a diesel. Lead was used for this in the past. The additional fastenings I posted earlier are not hard to install and do a good job.


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## Solandri (Sep 7, 2012)

hellosailor said:


> The lead/vinyl absorbs energy just because it is so dense. The foam decouples that vibration from the engine compartment walls, and in theory you get less noise.


The lead/vinyl for the most part doesn't absorb the energy. Its purpose is to create a density change which reflects sound back into the engine compartment. Both density transitions (air to lead/vinyl, and lead/vinyl to foam) reflect sound. The foam also creates a third density change (foam to fiberglass) which causes an additional reflection. The foam does absorb energy as you explain, but its primary purpose is to create additional density changes and thus additional reflections. Each reflection means less sound that's leaking out of the compartment.
Reflection and Transmission

This is also the reason that certain fish without swim bladders (e.g. tuna) don't show up well on fishfinders. Muscle is almost the same density as water, so without much of a density change there isn't much echo for the sonar to pick up. A swim bladder OTOH (muscle to air to muscle) creates a big echo.


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## deniseO30 (Nov 27, 2006)

Best way to soundproof engine compartment = sail more!


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## lillia28 (Aug 12, 2011)

Before you buy do some web searches on sound deadening. There's lots of info on sound transmission for the guys building 1000 watt stereos in their cars. The auto sound deadeners aren't cheap, but they are usually less expensive than marine stuff. I am in line for replacing mine also, so I've been looking.
Lou


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## mitiempo (Sep 19, 2008)

Remember it should be fireproof.


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