Adding Foam To Engine Cowling to Absorb Sound

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Author Topic:   Adding Foam To Engine Cowling to Absorb Sound

Wasatch Whaler posted 07-14-2008 09:55 AM ET (US)
I'm curious if anyone has replaced the foam inside their engine cover with a sound absorbing material like Dynamat? Would Dynamat or a similar product reduce the amount of engine noise?
TC Goldman posted 07-14-2008 11:02 AM ET (US)
I almost did the same thing, but I wasn't sure so I just left the old. Good Question. I hope someone has tried it.
JMARTIN posted 07-14-2008 12:32 PM ET (US)
I replaced my foam some sort of supposedly sound reducing matting. It is silver on one side and looks like carpet felt pad on the other and is about 1/2 inch thick. I am disappointed with the result and it does not shed water as well as foam. John
jcrwshw posted 05-22-2012 03:34 PM ET (US)
Hi Gang. I just finished soundproofing my 1996 Johnson 150-HP--wow what a difference! I used a product similar to Dynamat. The sound level was cut to a point where I don't need ear muffs. http://www.b-quiet.com
I would have to estimate a one-third reduction using the butyl rubber and then the 1/2-inch foam on top. Awesome stuff!
jimh posted 05-24-2012 07:31 AM ET (US)
Sound-absorbing foam will help suppress high-frequency noise transmission, but it has little influence on low-frequency sound transmission.
davej14 posted 05-24-2012 09:03 AM ET (US)
The transmission loss specifications for this product at 125 Hz is stated as 15 db. I would say that is a pretty low frequency and definitely would be noticeable.
thegage posted 05-24-2012 10:04 AM ET (US)
Hey jcrwshw,
Which specific b-quiet products did you use?
John K.
jimh posted 05-24-2012 01:05 PM ET (US)
How much thickness (and which product) has a transmission loss of -15dB at 125-Hz? That is a significant change. It would certainly be noticeable.
To appreciate sound levels measured in decibels, you can approximate one decibel change as the amount your kid will turn down his music player when you yell at him to turn it down; he turns it down 1-decibel, or the minimum noticeable change.
davej14 posted 05-24-2012 02:24 PM ET (US)
Here is the link, look at B-Quiet Vcomp material which is 3/8" thick:
http://www.b-quiet.com/compare.html
I haven't tried it personally but based upon the specifications and the first hand experience of jcrwshw, it looks promising. I would like some more first hand accounts if there are any out there.
jimh posted 05-24-2012 04:03 PM ET (US)
Well, of course the B-Quiet Vcomp material cited has good low frequency suppression; it's lead, not foam. As I said, foam will not suppress low frequency sound. You'll be wrapping your outboard motor cowling with a layer of lead. It weighs one pound per square foot; you'll be adding some weight, too.
kwik_wurk posted 05-24-2012 05:02 PM ET (US)
I have seen big improvements with higher quality sound proofing materials (mine was mylar/foam/vinyl/foam ~1lb/1ft^2). However never done a cowling. I suppose I could try as I have plenty of materials.
I re-did 80% of the engine room on one of my I/O's a few years ago. I could not hear the engine running at idle, in fact you had to look at the gauges or the exhaust to see if engine was running. The first time I took the boat out after the insulation job I was shocked that I could hear the noise that comes from the impact zone on the forward portion of the hull.
However in sound dampening the most common issue is air gaps. Closing and baffling all airways and gaps is the first big step. I re-did all the gaskets, and drawers so they would seal up and not transmit sound. -- Then I went on and did the insulation.
davej14 posted 05-26-2012 12:34 PM ET (US)
The Vcomp material does not mention lead as part of the sandwich:
http://www.b-quiet.com/vcomp.html
The Lcomp material does specify lead but also the website states it is not available due the the increased price of lead. Since the weight of each material is the same I have e.mailed the manufacturer for clarification.
contender posted 05-26-2012 05:15 PM ET (US)
I know it would be very hard to control but what about a spray foam used for insulation. This would coat the entire inside with a one piece foam with no voids, cracks, or cuts
davej14 posted 05-26-2012 07:12 PM ET (US)
I don't think spray foam would do much, sound absorbent foam materials are quite different. The other issue I can think of with spray foam is that it would probably not hold up to "under Hood" temperatures and it would age quickly.
JMARTIN posted 05-27-2012 12:59 PM ET (US)
My 1992 Evinrude 200's cowling is designed with air holes. With the original 1/4 inch of foam, it was loud. With my replacement 1/2 inch of foam blanket like stuff, it was loud. It's bare cowling now and it's loud but not louder.
John
contender posted 05-27-2012 01:09 PM ET (US)
Dave good point, what about coating the foam with something after the spraying it to the bare cowling...
pcrussell50 posted 05-28-2012 02:48 PM ET (US)
A little OT, but I wonder how many folks who are obsessed with boat motor noise, have added Dynomax or Flowmaster mufflers, or fatter exhaust systems to their trucks? Or louder-than-stock, pipes to their Harley's. More than one, I guarantee it.
-Peter
davej14 posted 05-29-2012 09:00 PM ET (US)
Here is some interesting information from B-Quiet in response to my e.mail inquiry:
====================================================
There is no lead in the Vcomp. We have actually discontinued our Lcomp (lead-based material) and we no longer make it. The Vcomp is made out of a dense 1/8" vinyl based polymer barrier with a 1/4" thick foam decoupler. It has a total thickness of 3/8", weighs approximately 1 lb/sq. ft.
When using this type of sound deadening product in boats, there are a couple of
things to consider.
1. B-Quiet Ultimate is the best sound deadening product available when it comes
to vibration reduction, resonances and noise traveling through the metal of the
boat. IT also has the highest heat rating which means it can go closer to the
engine.
2. B-Quiet Vcomp is the best product when it comes to deadening sound like road,
water and engine noise. But the Vcomp has a lower heat rating and CANNOT be used
as close to the engine. The Vcomp is also partly open cell foam which means if
it gets wet it will hold moisture and is not made for that kind of wear. The
best spray adhesive for use with the Vcomp is the 3M Spray 90 which will give
you a strong hold.
3. Hliner is good for stopping and absorbing engine noise as well but does not
have a rubberized polymer barrier. As well, It can hold moisture which can
create problems as well as wear out the material.
All three products should not regularly get wet but will provide you with
excellent sound deadening in different applications.
Thank you for your interest in B-Quiet sound deadening materials. If you have
any further questions please call or email us.
======================================================

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Author	Topic: Adding Foam To Engine Cowling to Absorb Sound
Wasatch Whaler	posted 07-14-2008 09:55 AM ET (US) I'm curious if anyone has replaced the foam inside their engine cover with a sound absorbing material like Dynamat? Would Dynamat or a similar product reduce the amount of engine noise?
TC Goldman	posted 07-14-2008 11:02 AM ET (US) I almost did the same thing, but I wasn't sure so I just left the old. Good Question. I hope someone has tried it.
JMARTIN	posted 07-14-2008 12:32 PM ET (US) I replaced my foam some sort of supposedly sound reducing matting. It is silver on one side and looks like carpet felt pad on the other and is about 1/2 inch thick. I am disappointed with the result and it does not shed water as well as foam. John
jcrwshw	posted 05-22-2012 03:34 PM ET (US) Hi Gang. I just finished soundproofing my 1996 Johnson 150-HP--wow what a difference! I used a product similar to Dynamat. The sound level was cut to a point where I don't need ear muffs. http://www.b-quiet.com I would have to estimate a one-third reduction using the butyl rubber and then the 1/2-inch foam on top. Awesome stuff!
jimh	posted 05-24-2012 07:31 AM ET (US) Sound-absorbing foam will help suppress high-frequency noise transmission, but it has little influence on low-frequency sound transmission.
davej14	posted 05-24-2012 09:03 AM ET (US) The transmission loss specifications for this product at 125 Hz is stated as 15 db. I would say that is a pretty low frequency and definitely would be noticeable.
thegage	posted 05-24-2012 10:04 AM ET (US) Hey jcrwshw, Which specific b-quiet products did you use? John K.
jimh	posted 05-24-2012 01:05 PM ET (US) How much thickness (and which product) has a transmission loss of -15dB at 125-Hz? That is a significant change. It would certainly be noticeable. To appreciate sound levels measured in decibels, you can approximate one decibel change as the amount your kid will turn down his music player when you yell at him to turn it down; he turns it down 1-decibel, or the minimum noticeable change.
davej14	posted 05-24-2012 02:24 PM ET (US) Here is the link, look at B-Quiet Vcomp material which is 3/8" thick: http://www.b-quiet.com/compare.html I haven't tried it personally but based upon the specifications and the first hand experience of jcrwshw, it looks promising. I would like some more first hand accounts if there are any out there.
jimh	posted 05-24-2012 04:03 PM ET (US) Well, of course the B-Quiet Vcomp material cited has good low frequency suppression; it's lead, not foam. As I said, foam will not suppress low frequency sound. You'll be wrapping your outboard motor cowling with a layer of lead. It weighs one pound per square foot; you'll be adding some weight, too.
kwik_wurk	posted 05-24-2012 05:02 PM ET (US) I have seen big improvements with higher quality sound proofing materials (mine was mylar/foam/vinyl/foam ~1lb/1ft^2). However never done a cowling. I suppose I could try as I have plenty of materials. I re-did 80% of the engine room on one of my I/O's a few years ago. I could not hear the engine running at idle, in fact you had to look at the gauges or the exhaust to see if engine was running. The first time I took the boat out after the insulation job I was shocked that I could hear the noise that comes from the impact zone on the forward portion of the hull. However in sound dampening the most common issue is air gaps. Closing and baffling all airways and gaps is the first big step. I re-did all the gaskets, and drawers so they would seal up and not transmit sound. -- Then I went on and did the insulation.
davej14	posted 05-26-2012 12:34 PM ET (US) The Vcomp material does not mention lead as part of the sandwich: http://www.b-quiet.com/vcomp.html The Lcomp material does specify lead but also the website states it is not available due the the increased price of lead. Since the weight of each material is the same I have e.mailed the manufacturer for clarification.
contender	posted 05-26-2012 05:15 PM ET (US) I know it would be very hard to control but what about a spray foam used for insulation. This would coat the entire inside with a one piece foam with no voids, cracks, or cuts
davej14	posted 05-26-2012 07:12 PM ET (US) I don't think spray foam would do much, sound absorbent foam materials are quite different. The other issue I can think of with spray foam is that it would probably not hold up to "under Hood" temperatures and it would age quickly.
JMARTIN	posted 05-27-2012 12:59 PM ET (US) My 1992 Evinrude 200's cowling is designed with air holes. With the original 1/4 inch of foam, it was loud. With my replacement 1/2 inch of foam blanket like stuff, it was loud. It's bare cowling now and it's loud but not louder. John
contender	posted 05-27-2012 01:09 PM ET (US) Dave good point, what about coating the foam with something after the spraying it to the bare cowling...
pcrussell50	posted 05-28-2012 02:48 PM ET (US) A little OT, but I wonder how many folks who are obsessed with boat motor noise, have added Dynomax or Flowmaster mufflers, or fatter exhaust systems to their trucks? Or louder-than-stock, pipes to their Harley's. More than one, I guarantee it. -Peter
davej14	posted 05-29-2012 09:00 PM ET (US) Here is some interesting information from B-Quiet in response to my e.mail inquiry: ==================================================== There is no lead in the Vcomp. We have actually discontinued our Lcomp (lead-based material) and we no longer make it. The Vcomp is made out of a dense 1/8" vinyl based polymer barrier with a 1/4" thick foam decoupler. It has a total thickness of 3/8", weighs approximately 1 lb/sq. ft. When using this type of sound deadening product in boats, there are a couple of things to consider. 1. B-Quiet Ultimate is the best sound deadening product available when it comes to vibration reduction, resonances and noise traveling through the metal of the boat. IT also has the highest heat rating which means it can go closer to the engine. 2. B-Quiet Vcomp is the best product when it comes to deadening sound like road, water and engine noise. But the Vcomp has a lower heat rating and CANNOT be used as close to the engine. The Vcomp is also partly open cell foam which means if it gets wet it will hold moisture and is not made for that kind of wear. The best spray adhesive for use with the Vcomp is the 3M Spray 90 which will give you a strong hold. 3. Hliner is good for stopping and absorbing engine noise as well but does not have a rubberized polymer barrier. As well, It can hold moisture which can create problems as well as wear out the material. All three products should not regularly get wet but will provide you with excellent sound deadening in different applications. Thank you for your interest in B-Quiet sound deadening materials. If you have any further questions please call or email us. ======================================================