sound proofing I/O

[oops!]

im restoring a 19 foot older sea ray.
4.3 merc I/O. alpha one drive. standard marine exaust manifolds.
the boat formerly used a "dog house" type motor housing. with two jumper seats on each side of the housing.
i intend on building a fiberglass dog house and sound enclosing the whole motor. in the past i have used thick pink foam, also aluminium backed fiberous colth??? accoustic celing tiles.
all trying to cut sound volumes. all with limited sucess

Question,
what is the thinnest, lightest, water resistant material for sound proofing an engine compartment?
unless im at WOT. i dont want to hear the motor.

thanks
oops

 

[orion25]

Re: sound proofing I/O

Take a look at Dynamat. It is used in Car Audio applications. It is not cheap though. Or you could spray the inside with rubberized undercoating (like the stuff under a car) or apply a spray in bedliner material in it (like Rhino Lining).

 

[oops!]

Re: sound proofing I/O

money isint the issue
and thats a great idea!

thanks!
oops

 

[JustJason]

Re: sound proofing I/O

I have dynamat underhood soundproofing liner, for cars, and it works good. the glue that's on the back of it doesn't take to rough glass. You'll have to use some carpet glue to get it to stick. that's what i do.

 

[PondTunes]

Re: sound proofing I/O

Another route you might look is a product by cascadeaudio I recently was looking for a solution to vibrations on a pontoon boat the offer spray on, or brush on as well as adhesive backed products that are designed for marine use. I also found it to be cheaper than buying dynamat and imo a superior product thus it is what I recommend & sell to my customers.

"http://www.cascadeaudio.com/marine/marine_sound_dampers.htm

More information can be found at their website above but either the roll on or the VB-2HD is what I would recommend for your project.

 

[amynbill]

Re: sound proofing I/O

Inside my engine compartment is acoustic egg crate foam (if this is the proper terminology?) similar to what is used in recording studios.

The engine was pretty damn quiet compared to what I thought it would be. I seem to remember my parents boat being pretty loud years ago in comparison.

 

[RWilson2526]

Re: sound proofing I/O

Basically you have two different ways to reduce noise contained inside and enclosure. First is through absorption . Different materials are rated by an "absorption coefficient" you want your number to be as close to 1.0 as possible. A good 3-4 # per cubic foot industrial insulation works well. The pink stuff for houses is generally very light and can be improved upon with the heavier industrial felts. The second way is through mass. The heavier the mass the the better the "transmission loss" of sound through it. Unfortunately with mass comes weight so a practical limit I guess must be established. I you can take the weight a good 1-2 # per sq foot lead impregnated vinyl material would work well.

If I really wanted to make my engine cover sound proof I would increase the mass of the fiberglass shell by glueing lead sheet or a lead impregnated vinyl material to the inside (1-2 lbs per sq ft) and then install 1-2" of a 3#-4# /cubic foot insulation over it. To protect it all from oils and damage I would then install a steel perforated sheetmetal over it. It would be expensive and heavy but it would be darn quiet.

 

[old-gubbins]

Re: sound proofing I/O

I guess dynamat is "lead impregnated vinyl material". I have used it on the front of the engine well of an outboard boat, and am pleased with it. It cut down the amount of noise resonating around the boat considerably, especially in the cuddy cabin.