Sound Proofing Diesel Engine Box

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Hugs Tug

Well-known member
May 30, 2006
Reaction score
Greenport Long Island N.Y.
Question for the Gurus,
2002 2510 with the 4.2 D Tronic diesel coupled to a Bravo 3 out drive.
Is there a better way to sound proof the engine box?
The original insullation is for from sound deadening. The material is about one inch thick and given the ehgine size there is not a lot of room to install more.
Has anyone peeled off the original and replaced with better. This is the only glitch that the owner has with the boat.

Thanks in advance
My insulation is still very much intact so it has not been replaced. I always figured that putting something over the two access doors on the transom would block out a lot of the noise because closing the door to the cabin helps a great deal. I think that the noise is blasted forward off the transom through those doors like they were speakers, aimed forward. Some of the noise may be tranmitted where the cockpit drains are. Probably have to
insulate that area too. I think there was some lead insulation at one time for this purpose. It would be hard to insulate some of the areas unless the hull cap was not there.

If you have ever been in a Sportsfishing boat, they are loud too. Can't hardly stay in the salon, underway. Just the nature of a diesel. A lot of the noise is from the air intake. The filter/cleaner is not silenced as in a car or truck. Putting a large bucket over the intake, may eliminate some of it. Lot of turbo noise too. Don't think just adding insulation will solve the problem. Sure would be a problem if it fell into the engine.

After awhile he will just not hear it anymore. Can he say, Huh?
Here's what I'd do ... I'd strip off the old foam and "paint" the box/well inside with Silent Running, a new sound-aborbing paint that seems to work really well, see their site here.


Here's a test report as a PDF file from Powerboat Reports:

Then I myself would probably also add some sound deadening foam made for the marine environment on top of that.
Here is my original insulation on a 5.7L gas engine on the inside of the engine cover. See if it looks like what was on the diesel.

I also second what Dale posted about the paint on product. Don't know anyone that used it but you can coat the vertical walls and the bilge as well.



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That is the same soundproofing. For some reason I cannot fathom how a painted application will work. Going on the web and research the product and see if they offer technical support.
I don't know if you changed our soundproofing yet but I did allot of research and consulted with several diesel boat owners. I found the best thing is to remove the 1" soundproofing and replace with 2" soundproofing here ... sq-ft.html.

From that same site, I also purchased 1/4" mass loaded vinyl. I am going to line the back of the entire transom wall with that. I already put it on back of each transom hatch door and covered the holes in each door with small pull rings.

The next project will be building a channel over the scupper holes which allow direct engine sound to radiate out. I am planning on using starboard with mass loaded vinyl on top. It will have to be removable to allow clean out the scupper well.

I will send more pictures as I progress.



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Here is a pic of how I replaced the 1" soundown with 2" 2lb/sqft. I left the 1" that I added when I first got the boat along the bottom of the box to allow for the deck flange.

The second pic is of the boxed in scupper channel I made with starboard and 1/4" vinyl soundproofing. I also lined the inside of the transom wall with the 1/4" vinyl soundproofing.

It is much quieter now but I am still going to line the forward wall of the engine box with the 1/4" vinyl soundproofing.


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