Engine sound deadening....

[Paul - SW Ontario]

The market's best is believed to be Dynamat, but wow, is it pricey...

Has anyone found a cheaper alternative with a noticeable difference in engine noise through the cockpit sole?

My Trojan has the factory teak sole, and I would like to adhere to both the engine cover, and the port and starboard helm areas...maybe even the staircase bulkhead.

Regards, Paul

[WayWeGo]

I am also interested in sound deadening options. The 40 year old insulation on our boat is falling apart and it is time to rip it all out and replace with something more current.

Something that insulates the cabin from engine heat is also a big consideration for us.

[Paul]

Hi Paul,
I started working on this exact problem a couple of years ago in the rear of the cockpit where it was easiest to access. The undersides of the cockpit floors already had some sound proofing done to them but I found that the open areas between the cockpit liner and the outer hull acted as an echo chamber which is made engine/generator noise worse. By blocking off these areas in the rear cockpit with soundproofing, it reduced the sound of the generator dramatically. This year I have the fresh water, black water and hot water tanks removed which gives me access to these areas in the forward cockpit for soundproofing.

Below is a picture of the area between the cockpit liner and the outer hull.

IMG_1162.JPG (56.18 KiB) Viewed 11790 times

Below is the picture of a piece of the material that I used. I don't recall the brand however it's about an inch thick and the back side is peal & stick.

IMG_1159.JPG (53.3 KiB) Viewed 11790 times

Below is a picture of the area blocked off with sound proofing as well as half way down the hull.

IMG_1163.JPG (58.92 KiB) Viewed 11790 times

I've also done the forward bulkhead in the engine bay to help keep noise down in the cabin when the generator is running. I'm fairly confident that my efforts will result in a quiet boat this upcoming season.

[Paul - SW Ontario]

Hey Paul, thanks for the pics and info...

Does that product in the pic have any kind of integrated sound deadening rubber/ poly type layer?

Been reading a lot about the principles of sound proofing. Apparently the combination of foam and rubber layers are the key.

[Paul]

Hi Paul,
Doesn't have a specific rubber layer, its made up of chopped foam and what seems possibly like neoprene rubber. I'll find out what the brand was and let you know. I can tell you that it comes in approximately 2' x 3' sheets and I think that I paid 30 something a sheet.

[mikeandanne]

Here is what I used, can't remember the name though, comes in sheets or a roll and is heavy.This is fire rated and works for heat and sound.

[The Dog House]

I used Dynamat under the cockpit floor and it lowered the sound levels considerably. Before the Dynamat installation I could not hear my exhaust, only the engine noise coming through the cockpit floor. After installing the Dynamat about 80% of the sound I hear is from the engine exhaust and 20% of the sound is from the engine coming through the floor. The Dynamat is expensive but it does work very well.

[Paul - SW Ontario]

I used Dynamat under the cockpit floor and it lowered the sound levels considerably. Before the Dynamat installation I could not hear my exhaust, only the engine noise coming through the cockpit floor. After installing the Dynamat about 80% of the sound I hear is from the engine exhaust and 20% of the sound is from the engine coming through the floor. The Dynamat is expensive but it does work very well.

Appreciate your input....good to hear actual results of Dynamat on a Trojan application.

Did you install it under the entire cockpit floor or just the engine cover?

[The Dog House]

Did you install it under the entire cockpit floor or just the engine cover?

The 1971 engine cover is probably half of the cockpit floor area due to the V drive configuration. I used Dynamat on about 2/3 of the engine cover (concerned about clearance directly over the spark arrestor). I also used Dynamat on about 1/3 of the underside of the non-engine cover cockpit floor. The total coverage underneath the total cockpit floor area was around 50% (2/3 of 50% + 1/3 of 50% = 50% of total).

According to the Dynamat instructions, Dynamat is not a barrier but an absorber (converts sound energy into heat energy). It will therefore work just as well when mounted on vertical walls in addition to underneath the cockpit floor. Because of cost I just mounted it under the cockpit floor where there was access. I started with the engine cover and then used what was left over underneath the other parts of the cockpit floor. I ran out before I could start mounting it on the vertical walls. The reduction in engine noise was enough that I didn't feel it was necessary to buy more.

[Paul]

Hi Paul,

The material that I used is from "QL Marine Accessories" which is a division of Volvo Penta. These sound absorbent panels are available in several different thicknesses.

Hope this helps

[Paul - SW Ontario]

Hi Paul,

The material that I used is from "QL Marine Accessories" which is a division of Volvo Penta. These sound absorbent panels are available in several different thicknesses.

Hope this helps

Excellent, yes it does....Thank you!

[AlphaJustin]

Am I late to this party? The trend in automotive lately is spray on bed liner it deadens the sound and is very easy. Will it work on boats? Idk but I don't see why not.