Re: Sound deadener?
The original sound deadening foam insulation in my cover has deteriorated to the point that it's gone. The engine isn't unbearably loud, but I'd like to try and quiet it down a bit. Someone here mentioned they used some 1/4" insulation board they got at one of the home improvement stores, but I can't find 1/4" anywhere. I was thinking about trying the spray-on rubbery type stuff, but wanted to hear what others have done, or if they have tried this stuff. If you've used it, are you satisfied, and how thick or how many coats did you use?
Thanks!
I went through this process several years ago, and I'll try to relate my memory of what I learned.
First, as you probably know, the huge majority of the engine's noise comes out of the prop hub with the exhaust. There's nothing you can do about that.
Therefore, any improvement you make will be at the margins - you can make improvements, but it will be an improvement on only a small portion of the sound, therefore probably not as much effect as you'd like.
One of the basics is that the amount of sound deadening depends a lot on your ability to TOTALLY seal off the area. A house door that is fully closed deadens sound from the next room a huge amount more than a door that is only slightly ajar. On an outboard, you cannot completely seal the cowlign because there are air vents designed in and you can't block them.
Therefore, that also (along with the source of the sound) decreases what you can do.
Finally, the material has to do more than just take up space. It isn't nearly the same as heat/cold insulation which is just a matter of dead air - which is why simple foams work well for temp. insulation. They won't work well for sound deadening, because the material actually has to halt or dampen the sound waves. This genearlly means that sound deadening material has a layer of some dense material - like a laminate of lead or heavy vinyl. This is why the types of foam you can get at home depot, etc. won't do much for you.
Aaaalllllll that said
... I found an online source of material for lining the doghouse of an inboard engine, and they also sell "outboarder kit" for an outboard. I think I might have just bought the material in bulk because I did a couple of engines. The material is a foil faced foam with a layer of heavy vinyl. It had a peel off adhesive on it but could also be attached with spray adhesive.
I just did a quick websearch for "outboarder kit" and this looks like the stuff I got - but I can't remember if I bought it from them or some reseller (like Cabelas, Overtons, Basspro, Iboats, etc). You might check.
http://www1.shore.net/~dobquiet/
It made a noticable (to me) difference in the sound level but I doubt if the casual listener would all of a sudden say - "man that's a quiet outboard!" I thought it was worth while, but definitely just made a marginal improvement.
