Engine noise insulation

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AussieCraig

AussieCraig

Senior Member
Joined
May 16, 2013
Messages
179
Location
USA
Vessel Name
The Salty Swallow - named by wife
Vessel Make
Private builder - 50' Trawler
I am seriously considering 'boxing in' both the 671 and the generator with a wooden frame and some sound insulation...I did a search and read what was already on the site but decided to see if anyone had any recent updates on what is available as far as sound deadening panels or other ideas to cut the transference of engine noise to the cabin...

There is a foil faced sheet of some sort of insulation already lining the roof of the engine room however some further reduction would be great....anyones experiences would be appreciated !
 
Greetings,
Mr. AC. Even not knowing the layout of your ER, I would be hesitant to "box in" a piece of machinery that I would have to access on a daily basis (fluid checks, repairs, emergency actions etc.). Might you be better to increase the engine roof soundproofing?
 
Hi Craig,
I've got the same project on my to-do list. It appears most of the effective noise reduction panels have a thin sheet of lead or similar in them. The mass is required to absorb the low end frequencies. There are spray on products, although I am not sold on them.
It appears any decent material is fairly expensive (and heavy). About $80 (and 10 lbs) for a 3ft x 4ft sheet from our local marine suppliers.

It is also very important to ensure your hatches are well fitted. A small gap can transfer a lot of noise.

Besides reduced access as RTF mentioned; boxing in an engine too much may cause overheating issues.
 
I should have elaborated a bit, the boxing in would entail panels that could be lifted off and away giving full access to the engines. I agree with you Auscan, it appears you get what you pay for and it won't be cheap....
 
Most genset makers offer a sound shield, which suggests it is ok to have one,which you could replicate DIY. Depending what the original costs.
Boxing in the main engine sounds more problematic, but think of older boats where the engine protruded into the saloon and a box over it became a table. Recently we were in Scotland aboard a converted trawler with a boxed over engine in the cockpit. Even so, heat dissipation must be an issue, and if you vent the box you`ve got noise.
 
Engines have mufflers on them usually on the exhaust only. Take the air cleaner off your car and you'll experience a lot of intake noise. Especially when you "stick your foot in it". On a diesel engine there is no throttle valve to shut out the intake noise at low throttle openings as the intake tract is always wide open.

Some marine engines have next to no intake muffling hardware. So it seems to me that large reductions in noise, especially right above the engine/s (like the main salon in one's boat) would be at least worth thinking about.
 
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You need to check with the engine manufacturer to determine how many cubic feet of air the engine requires.
4 3" diameter holes was enough air for my cat 3208.

You will need to vent the box. A fan to suck the heat out more than likely.

Better to insulate the overhead. Go in the ER and turn off all the lights where you see light coming in sound gets out.

SD
 
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I would not enclose the engine but sound proof the engine room and or better muffled exhaust system. Being The Eagle engine room is pack with stuff that absorbs noise, the engine room is carpeted, a new improved muffle exhaust, and the salon is carpeted it a lot quieter than when we original bought the boat.

There are ways quiet the engines.
 
Have a friend with a single 671 and he had a "sound blanket". heavy sound suppressing material, suspended on wires just over and around the engine, perhaps 8-10 inches. I was never convinced it did a lot of good, but he claimed it made a measurable difference. Since he is an engineering type-I take his word for it.
 
We have a factory built sound shield on our generator. The service points are all on one side so only one panel needs to be removed for routine service/inspections. The air intake is a baffled so the sound reflects off of the sound deadening material. For quick checks such as oil and the water pump, there are 2-4" inspection plates. Our sound shield does what it is suppose to. :thumb:
 
In the old days w my 17' OB cruiser I started out one morning and after it warmed up I took off my coat. A rather large coat. I looked around for someplace to throw it and saw the engine back there humming away. I threw the coat over the engine and was amazed at how quiet it suddenly became. I ran a lot after that w that coat over the engine .. a 35hp Johnson.
 
There is also the magical cork panels, light weight, cheap and can be coated with noise reducing coats like Mascoat Delta Db. Can be glued onto existing insulation, onto the fuel tanks, the engine bed and hull. This will be a cheap solution.

Reducing engine vibrations to the hull is also important - Isoflex engine mounts (Australian as far as I know) makes specialized mounts and they are reasonble in price.
 
I'd recommend Sounddown..as noted in post #12. You might consider their acoustic carpet underlay as a first step if you have a carpeted salon...otherwise if you have inadequate ER lining, pull out and use the heaviest Sounddown panels you can afford.
 
Sounddown is good - no question about that.

But, 6mm of cork would reduce the sound with 10-15 Db as per some experts. That's a lot of sound reduction for very little thickness. Or maybe add 6 mm more for even better result. It is glued onto the existing surfaces / existing insulation and will therefore be a much easier fix compared to replacing or adding Sounddown, which probably would require a lot of equipment to be removed before the Sounddown can be installed.
The carpet underlay is a good idea though and would probably be first on my list.
 
Searios said:
There is also the magical cork panels, light weight, cheap and can be coated with noise reducing coats like Mascoat Delta Db. Can be glued onto existing insulation, onto the fuel tanks, the engine bed and hull. This will be a cheap solution.

Reducing engine vibrations to the hull is also important - Isoflex engine mounts (Australian as far as I know) makes specialized mounts and they are reasonble in price.
Click to expand...

Excellent points, the air intake for the 671 is an uninsulated metal pipe so some lagging around that would help and I will check the engine mounts - from memory they may be solid...

There are also many reflective surfaces in the ER itself that could be insulated...and cork stick ons may do the trick...:dance:
 
@ Aquabelle and Searios, I will be replacing the carpet with sheet flooring asap so underlay will be part of that job. I will also see if I can find some 'cheap' cork tile to attach to the existing ER roof insulation....I will take some pics and report on the effectiveness once done...
 
Cork rolls are preferable to cork tiles - but not so easy to get and more difficult to handle -

I'm using 6mm cork rolls glued onto the underside of my floors, facing the bilges. This should give better insulation, reduce possible sweating of the floor steel stringers and also reduce wave slapping noise (I hope)...

I might even add cork on my floor over the engine room as well.
 
The idea to carpet the engine room floor is a good one - reduces noise, eases the pain on the knees and knuckles, tools and bits stay put if the boat is rolling and it absorbs smaller amounts of water or fuel before it goes into the bilge.

I will consider that on my boat.
 
I would not carpet anything in my engine room unless they are now making suitable engine room carpet....

Certainly not with anything absorbent and definitely not permanent. There are soft mats that are easy on your knees and you can still wipe up spills or exhaust soot off of them and it won't retain the odor as badly.

Another consideration would be the fire hazard...yes a small one but still something that can be avoided by using more suitable materials.

I also would be careful of carpet underlayment unless it is closed cell and has a film surface over it. One high pressure diesel leak or exhaust leak and most foams would smell and become a fire hazard.

If you are willing to replace carpet or underlayment regularly or after every little spill, etc....then it certainly lessens the issues I mentioned.
 
psneeld said:
I would not carpet anything in my engine room unless they are now making suitable engine room carpet....
Click to expand...

I was wondering if anyone would mention that. To be honest though, I don't suppose flammability is an issue since the fumes created by even a small carpet fire would probably kill everyone before the fire became a problem.
 
I can't imagine how loud your engine must be to have to go to all this trouble to reduce the ambient sound! I have a Cummins 330B on my little boat and the sound actually "sooth's" me! I think that the sound from a Detroit 6-71 is one of the best (albeit loud) sounds in boating. It actually puts some people to sleep. :blush:
 
Searios said:
.... tools and bits stay put if the boat is rolling and it absorbs smaller amounts of water or fuel before it goes into the bilge.
Click to expand...
???????????? You are kidding, right? :blush:
 
Personally I wouldnt be putting anything on the ER floor...however cork or another sound absorbent on non horizontal sound reflecting surfaces as well as either boxing in the engines (with adequate and well designed ventilation) and or adding to the existing insulation on the ER roof sounds like the way to go...
 
SeaHorse II said:
I think that the sound from a Detroit 6-71 is one of the best (albeit loud) sounds in boating. It actually puts some people to sleep. :blush:
Click to expand...

Couldn't agree with you more on that Walt. My admiral on the other hand does not. Our compromise was the gasser with nice open exhaust.
 
Interesting thread.
Coming from sailboats, I really want to reduce engine noise throughout. Sure, there are plenty of soundproofing "sheet" materials out there, which the manufacturers attempt to market with features such as "self-adhesive" etc, but the fact remains, the engine room walls are cluttered with pipes, cables, pumps etc. etc. So, bearing in mind that there should be no gaps, without significant work - removal of ALL (wall, ceiling) fixed appliances - a tidy and successful soundproofing solution in the engine room surely cannot be achieved using sheet materials... Thoughts?
 
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