Best way to soundproof engine compartment?

FrankLanger · #1 (**permalink**) 01-14-2007

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.

bestfriend · #2 (**permalink**) 01-14-2007

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

sailingdog · #3 (**permalink**) 01-14-2007

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.

FrankLanger · #4 (**permalink**) 01-14-2007

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.

sailingdog · #5 (**permalink**) 01-14-2007

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.

FrankLanger · #6 (**permalink**) 01-14-2007

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.

sailingdog · #7 (**permalink**) 01-14-2007

Quote:

Originally Posted by FrankLanger

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.

hellosailor · #8 (**permalink**) 01-14-2007

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.

Faster · #9 (**permalink**) 01-14-2007

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.