Noise insulatiuon

dOb · Jan 21, 2013

I have a 1974 50hp Mercury. I've done some work on it and it runs well but at top speed is very loud. I was wondering if there is a method for insulating the wrap around cowling to reduce the noise. It has the original thin layer of insulation covered in plastic. But that was 1974, and I'm sure there are more efficient materials available today. Any ideas? Would better insulation in the wrap even help the noise level? Thanks.

mercurymang · Jan 21, 2013

Re: Noise insulatiuon

I'll be doing the same thing. You will more than likely get several different answers but dynamat may not be a bad option. Hopefully someone who has replaced it successfully will answer this one.

Maxz695 · Jan 21, 2013

Re: Noise insulatiuon

Alot of mercs make lot of noise when WOT but there also could be a reason or two it is seemingly loader than it should be. The Boot for the exhaust tube that sits on a spacer may need attention. I have seen the metal ones crack brake and fall to peices creating a gap which allows the exhaust to enter the midsection and making the engine much loader from the lack of the seal. I have seen the plastic space Toatally melt. I have seen the rubber boot also melt. There is also a gasket that is located between the exhaust plate and the exhaust tube that may be blown. Any place the exhaust tube is not properly sealed will seep into the midsection and not out the prop hence giving you a loud engine.

dOb · Jan 21, 2013

Re: Noise insulatiuon

That's worth looking into. I know that at the end of the summer I had the LU off to work on the water pump, and all seemed fine. I also had to replace the inner exhaust plate. The new one even had more baffling than the original and I replaced all of the exhaust gaskets and the gasket for the back cover ( the one that goes over the plugs). But it's always worth checking with this old motor.

Assuming that it's just a loud mercury, would insulating the wrap cowling even cut down on the noise?

chriscraft254 · Jan 21, 2013

Re: Noise insulatiuon

I used this stuff on my engine cover for my I/O. Its a third of the cost you will pay for dynomat and is made up of the same materials basically. Its very easy to install, self stick, cut with scissors or razor knife. You can find it at Lowes in the roofing isle.

My engine cover after wrapped.

Maxz695 · Jan 21, 2013

Re: Noise insulatiuon

Yes any insulation should cuy the noise down. On some motors like my 70 there isn,t much room for it I would suggest to at least add some inside the the front cover.

quicktach · Jan 21, 2013

Re: Noise insulatiuon

You may want to try HTArmaflex made by Armacell. Google them.

dOb · Jan 22, 2013

Re: Noise insulatiuon

Great. Thanks. This gives me something to think about. I'll post back here when I get a plan. Maybe I can do a before and after video to see how much noise reduction I actually achieve.

mercurymang · Jan 23, 2013

Re: Noise insulatiuon

chriscraft254 said:
I used this stuff on my engine cover for my I/O. Its a third of the cost you will pay for dynomat and is made up of the same materials basically. Its very easy to install, self stick, cut with scissors or razor knife. You can find it at Lowes in the roofing isle.

My engine cover after wrapped.

How well did it cut the noise level?

chriscraft254 · Jan 23, 2013

Re: Noise insulatiuon

mercurymang said:
How well did it cut the noise level?

Quite a bit, I think part of that is due to me solidifying the engine cover as well though. I don't have a noise meter though and have not gotten a chance to take another video yet while running.

Chris1956 · Jan 23, 2013

Re: Noise insulatiuon

There is a mylar insulation that looks like bubble wrap. That may be a good choice.

mercurymang · Jan 23, 2013

Re: Noise insulatiuon

Chris1956 said:
There is a mylar insulation that looks like bubble wrap. That may be a good choice.

Yep. I've seen that and it does look interesting. Easy to get and relatively inexpensive.

BSnB · Jan 28, 2013

Re: Noise insulatiuon

chriscraft254 said:
I used this stuff on my engine cover for my I/O. Its a third of the cost you will pay for dynomat and is made up of the same materials basically. Its very easy to install, self stick, cut with scissors or razor knife. You can find it at Lowes in the roofing isle.

My engine cover after wrapped.

I used this same material on the hatch covers over my engine compartment. It has reduced the noise and vibration considerably. It is very easy to apply, as chriscraft254 says.

Fed · Jan 28, 2013

Re: Noise insulatiuon

There's an app for that.
I picked up a sound meter app for my little nexus tablet and I'm going to attach a tube, like a ball point pen case, over the speaker to make it directional then do some on water tests to see if I can find exactly where noise is coming from around my motor.

dOb · Jan 29, 2013

Re: Noise insulatiuon

I went to the Hardware store intending to buy a roll of ?Quick Roof.? When I got there, I saw a roll of the Mylar covered bubble wrap. I decided to go with the bubble wrap.

If it were a larger area, I think you would get better coverage with the quick roof. And I think it would be hard to get the bubble wrap to stick well. But for such a small area, I was able to use aluminum tape and it worked out fine.

The front cover had a small pouch with the pull rope in it. I just remade the pouch and put the rope inside. Hopefully I can get out next weekend and see if it makes a difference.

Thanks for all of the help.

Moody Blue · Jan 29, 2013

Re: Noise insulatiuon

That's a really nice job on that cowling. You used alum tape to stick the outer edges? Is the entire surface of the bubble wrap "stuck" to the cowling?

dOb · Jan 29, 2013

Re: Noise insulatiuon

Thanks. Just tape on the outer edges. I thought about using some type of cement on the back side. But that was partially why I went with the bubble wrap, I figure that it will be easy enough to remove if necessary.

dOb · Feb 17, 2013

Re: Noise insulatiuon

Quick follow up:
Finally made it out yesterday to test a couple of things. There was definitely a drop in the noise coming from the motor. At full throttle I was able to speak to my son at a pretty easy volume. Don't get me wrong, it still makes noise, but no near as much as before.
I considered adding a layer inside the top of the hat. I think it would help even more, but I'm concerned that if it came of, it would get chewed up by the flywheel and make confetti that would get into everything. I'm might try some 3M adhesive and see how strong it feels first. Either way, I'm happy with the results.

Chris1956 · Feb 17, 2013

Re: Noise insulatiuon

I would think a spray adhesive would hold that bubble wrap insulation whereever you want it. If not, contact cement certainely will.

KnarfOH · Mar 29, 2013

Re: Noise insulatiuon

dOb said:
I have a 1974 50hp Mercury. I've done some work on it and it runs well but at top speed is very loud. I was wondering if there is a method for insulating the wrap around cowling to reduce the noise. It has the original thin layer of insulation covered in plastic. But that was 1974, and I'm sure there are more efficient materials available today. Any ideas? Would better insulation in the wrap even help the noise level? Thanks.

Click EDIT LINK to see how I added sound deadening material to my 1984 Chrylser Force Engine outboard engine. It was GREAT. Obviously, what you are looking for is to reduce the noise. No way to cancel it out - but a lot of noise is the result of vibration and resonance.

Click EDIT LINK to see how I added sound deadening material to the engine cover of my 2007 Bayliner 175 BR (boat I purchased after selling my 1984 Bayliner Capri outboard).

Noise insulatiuon

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