Sound deadening for inboards??



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  • Sound deadening for inboards??

    So I'm looking for anyone who has done some sound insulating for their engine cover? I have a sportjon but all the covers are basically the same in design. I was considering the stuff they use for cars when doing speaker installations and such (i think it's called hushmat) I do know it's pretty spendy so was looking for any experiences or ideas bofore dropping a bunch of cash. Thanks
    " There's a fine line between fishing and standing on the shore like an idiot" - Steven Wright

  • #2
    Sound proofing

    I tried a few things when I installed an inboard diesel. Sounddown sound deading mats and silent running sound deading spray. These both helped but if I were to do only one it would be the sounddown mats. They are about an inch thick and have a tin foil finish. They are layered, foam,sound deading ruber, foam and tin foil.
    Mats can be cut with heavy duty scisors and glued on.



    • #3

      is the noisiest boat i have ever owned. you can dynomat the inside of the doghouse, might want to add a couple clamshells for ventilation and cooling. carpeting the outside of the doghouse would help too. also getting everything you can welded instead of screwed in would help alot unless this is done on yours already.


      • #4
        Sound Deadening for Inboards

        Call Hamilton Jet in seattle. Order barrier 104 and you can take a nap in the boat.I have a 25' Diesel and have sound deadening between every screw down panels and have barrier 104 in the engine area.I have a 315 h.p. Yanmar in it. Good Luck



        • #5

          Thanks all for the ideas guys. I'll check out the sounddown and barrier 104. Maybe then my wife and I can carry on a conversation on the river. Then again maybe the noise is a good thing. Just kidding. Thanks again.
          " There's a fine line between fishing and standing on the shore like an idiot" - Steven Wright


          • #6
            Great info, thanks

            Was just looking into sound deading stuff, I was wondering about the fire retardent propertys of some things on line.
            I added what they call a Fire Port, so I do not have to lift the cowling up to use the fire extinguisher. I just stick the nozzle in the break out hole and squirt. Saves from adding fresh Oxy to a fire and getting a huge flare up.


            • #7
              Fire port?

              Make sure its not steam from a melted riser boot leaking water or a smoked belt before you let her have it.


              • #8

                I used Soundown in mine but, haven't had a chance to test it out yet. I used 2lb/sq ft barrier but I think 1lb is easier to install. It is more flexible.

                Remember, sound travels through air. No foam will stop sound. You need something solid. They used to use lead. If you want to sound deaden a room you don't add insulation in the wall, you add a second layer of sheet rock.

                Soundown has a solid barrier sandwiched between two layers of foam. The barrier stops the sound and the foam reduces the vibration. You need to install it as if you were trying to make it air tight.

                27' x 9.5' Glacier Craft - Volvo 300hp D4 Diesel
                Remember: Any fool can be uncomfortable.


                • #9
                  Sound Deadening Material & Safety Aspects

                  Couldn't Google Barrier 104 but did find Dynomat. Two thing I looked at is the Chemical Resistance and Fire Rating. Dynomat did not have a Fire rating. Don't think I'd like to put a product that could put of a deadly cloud of smoke. Most people die from fumes not fire.
                  Dynoliner did have a HF-1 fire Rating
                  There product called Hood liner had the highest rating HBF;
                  (HBF is the highest possible classification) according to the strict US fire safety standard UL 94," says Schulz. This test includes checking whether and how fast a foam test piece burns when it has been exposed to a naked flame for a minute and whether material dripping from the test piece due to heat ignites a layer of cotton wadding.
                  Foam is a important to sound deadening; It's not true that Soild is better;
                  The effectiveness of an acoustic foam depends on its ability to convert sound waves into heat energy. Dynamic Control's Hoodliner has a combination of open and closed cells to accept and dissipate sound waves. If all the foam cells were open, sound waves would simply pass through. Conversely, if all the foam cells were closed, few sound waves would be absorbed. The acoustic foam in Hoodliner is cast in sheets for consistent resistivity levels throughout the foam, to assure maximum sound absorption.
                  If the material you install is going to absorb gas fumes it's not the right stuff.


                  • #10
                    the problem with my sportjon was that the engine was loud AND the whole boat vibrated with the motor. this was due to lightweight material ( which is handy when you are pushing the limits ) but transfers sound badly. not sure if you have the welded windshield but i reccomend it and whatever sound deadining you can install. im thinking they ought to come out with a hardtop series of sportjon. also msot sportjons are setup so close to the motor theres only so much you can do. id deaden the inside of the dogbox with whaterver you find best and in the budget, carpet the outside of the dogbox, and get rid of the screws holding metal to metal. add some clamshells for cooling and ventilation. the sportjon is an extremely capapble riverboat but noisy and built more for the capapbitlity than the luxury.


                    • #11
                      I hear you riverrat. I didn't buy the boat for comfort as much as function. I don't expect to ever get it as quiet as a four stroke outboard. If that had been my main concern, that's what I would have bought. Hopefully doing the doghouse will be an improvement. I do have the screwed on windshields but don't think I'll go so far as having them wleded. I was also thinking that if you put some foam in behind the carpeted panels on the stern and the ones around the bottom of the doghouse you should see some improvement there too. I've been talking to another SJ owner in Fairbanks who seems to have done quite a bit of experimentation in this arena. If I wasn't deployed right now I'd have already visited him to see what he's done to his. I'm just looking forward to getting home so I can get back on the water.
                      " There's a fine line between fishing and standing on the shore like an idiot" - Steven Wright


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