Cowling acoustic liner

[SiggiJo]

Has anyone ever tried or heard of installing acoustic liner inside the top cowling? I have a ´78 Rude 70HP and while it runs and sounds good, I was thinking that by lining the inside with a sound-deadening material, it could be made even quiter. It would have to be relatively thin, fireproof and moisture & mildew resistant. Do the newer motors have anything like this? On aircraft we use insulation blankets made of glass-wool, sandwiched between two layers of foil-type material. Perhaps that would work on an outboard?<br />And come to think of it, most cars even have some sort of insulation stuck to the inside of the hood...

 

[BoatBuoy]

Re: Cowling acoustic liner

If you can find Aquaplas, it might help. It was used by Altec-Lansing as sound-deadening in some of their audio equipment. Developed for use in/on nuclear subs for sound deadening. After application, it looks very much like auto undercoating.

 

[JasonJ]

Re: Cowling acoustic liner

I have considered getting some of that stuff they are using in cars now that applies in sheets. It is called Acoustimat or something like that. You just peel off the backing and stick it on, it works really well for those wanting to deaden their car for those high end stereo installs or just getting rid of road noise.

 

[Silvertip]

Re: Cowling acoustic liner

Check heating and air conditioning sources. There is a foil backed and very dense material used in that area to quiet ductwork and fan housings. You might also check auto supply and auto restoration sites as this stuff is also used under auto carpeting to quiet road noise.

 

[KIGuy52]

Re: Cowling acoustic liner

I once lined an old Merc with the insulation blanket material from a Huey that they let us strip before they crushed it. My mother spent several hours cutting and sewing it to fit. I attached it to the inside of the cowl with Velcro. Sadly, it made little or no difference in the noise. My guess is that Upinsmoke's material would work better.

 

[willamettejeff]

Re: Cowling acoustic liner

Don't overlook a motorwell if you have one as a large source of motor noise. Motorwell acts like a big speaker and resonates with the sounds and vibrations created the motor.

 

[Paul Moir]

Re: Cowling acoustic liner

My gut instinct is that the heavy thin sound deadening material (Dynamat, etc) is the way to go. But '60s era OMC larger 2 cylinder outboards used about 1" of open cell soft foam. They omitted it on the "economy" outboards, so I'm guessing it did something.<br />Unfortunately, the open cell foam made a great sponge for fuel & oil too.<br /><br />Mcmaster-carr.com has a wide selection of sound deadening materials if you want to get an idea of what's out there.<br /><br />EDIT: Sheet lead (used for flashing) might be the way to go. Just make sure there's no electrical contact between the aluminium parts of the outboard and the lead!

 

[JasonJ]

Re: Cowling acoustic liner

Dynamat is what I was thinking of...Thanx Paul.

 

[SiggiJo]

Re: Cowling acoustic liner

Hi guys, thanks for all your suggestions - I have now have plenty of options to weigh up - will let you know how it goes....