Optimax Cowl Sound Proofing

[flatsboy]

So I took the challenge to replace the cheap stock foam with the Dynaliner to see if it would work in my 2014 Optimax 250 Pro XS serial #2B016745.


So here you can see the removal of the stock foam. Use a putty knife and start on a edge and work the foam away slowly take your time as it can tear easily. You need this as a pattern so don't destroy it. And remember pattern both sides as they are opposite and you want the glue side down on the dynaliner when you make both patterns don't make that mistake!



The removed foam leaves the glue on the cowl mostly. Not to worry use mineral spirits with a brush and soak the residue left behind. Take your time here and let the mineral spirits do it's job let it sit for at least 10 minutes.Then use your putty knife to scrape the glue into a ball and remove. Do not wipe it up at this point it will just smear all over!





Once you get all the glue off clean the surface with denatured alcohol to get ride of any thing left behind. You want a clean surface to make sure the dynaliner has a good bond.





I used the 1/2 inch Dynaliner which is the same thickness as the stock foam. Don't use anything thinner as it won't have enough absorption properties. One pack of 1/2 inch which it comes in a 32 x 54 sheet will work for the three main pieces with a little left over to do some other areas as you can see. There wasn't enough to do the lower side pans so That din't get done but it would most likely help even more.





So I went and ran the boat yesterday after doing the Dynaliner to see how much it helped.
I can honestly say it did help deaden the sound at idle and the compressor isn't as annoying like before.Once running at 3000 RPM's it was a audible difference and where it really shined was at 5000 RPM's and over for sure without any performance issues other than noise suppression.
Now I'm not going to tell you it's as quiet now as a four stroke. But it did help suppress and dull the sound enough where it was noticeable. Was it worth it well I would say yes. I did get the Dynaliner for a deal at $56 bucks.The Dynaliner is a dense rubbery foam which is why it works better than the light see the light thru stuff that comes inside the cowl from the factory.
A little elbow grease and a few hours is all it took. The glue on the back of the Dynaliner is strong and will not fall down once applied for sure so no need to worry about using any other type of spray glue.It's designed to go into engine compartments and heat related areas.The dynaliner contores to the cowl with no problems at all and most likely will hold up better over time that stock.

http://www.dynamat.com/brands/dynaliner/

https://www.google.com/webhp?sourcei...20%2B%20prices

[neo]

Nice job!!

[Savage]

Looks good.

It would have been great if you had some before, and after decibel readings to compare.
How much weight did it add, since he foam is more dense?

[flatsboy]

Looks good.

It would have been great if you had some before, and after decibel readings to compare.
How much weight did it add, since he foam is more dense?

The whole box weight was just around 3 lbs. including the cardboard box it was in. The foam is light it's not like a mass load vinyl lead lined or anything like that but it was denser and had more mass that the stock stuff did and cuts with a sharp pair of scissors.
As far as DB level reading at idle since I'm a audio engineer by trade and own one currently. The DB drop were several decibel's but not enough to justify by taking pictures for a visual because that's not what really mattered.If I told you it dropped 5 to 10 DB who cares it's what you don't hear that really matters let me explain.
The real test was using my ears and the way it changed the tone of what was being heard while at idle and running. Frequencies are perceived by the human ear to our brain in different ways. So by altering and offsetting them into different energy ranges changes the volume and how they are transferred it's called tuning. Just because you lower the volume doesn't mean those resident frequencies won't still be heard.By absorbing them and there energy in a close proximity you kill them to the point so they don't transfer further away from the source compared to when it was in stock form and the lack of stock absorption.
What's really perceived and heard by our ears is the higher pitch frequencies that travel thru space faster and further than lower frequencies do.You may feel them as the motor is still vibrating on the transom which will never change. But you will not hear them as prevalent since your several feet away from the motor when running or at idle but was noticeable standing next to it also.Using a DB meter while underway would do no justice the reason being you have the wind to deal with and that would skew any test readings by the meter and you would see no difference at least with a hand held device.But the human ear will perceive it a different way which is what your really after here and it worked out well for me. Hope this explanation helps. I could go into detail more but it's not worth it nor do I see the need to. Try it out on your motor to see for yourself.

[swaddict]

nice work, might have to add that to my 'to do list'

[Savage]

Yep I understand.......thanks for the explanation Flatsboy!

[mdtritn21]

My question would be does it hold more heat under the cowl than standard foam since it's denser.

[flatsboy]

My question would be does it hold more heat under the cowl than standard foam since it's denser.

I would say look at what Mercury does to a a Mercury Factory Racing 300 Pro XS. Which uses 3/4 inch aluminium foil backed.If the foil backed doesn't increase it and create a oven inside I'm sure I'm good. Plus ran it in 90 degree at WOT 6100 and 73 MPH for 3 miles and did not overheat or increased in temperature to the motor.
As long as you do not obstruct the venting your OK.

Plus guys are running there motors with those motor covers on all the time.
http://www.tuffskinz.net/

I'm sure Don will comment and have something to add.

[fishnfireman]

Looks like a winner...... Mine is already so much quieter than the old racing engines I had not thought much about it... But the older I get-- the more I like silence >>>

[flatsboy]

Yep I understand.......thanks for the explanation Flatsboy!

[EuropeanAM]

Nice job and write-up.

[flatsboy]

Feel free to put it in a sticky under 3.0 mods if you like for the future.

[EuropeanAM]

Will do- remind me in a few days (there seems to be an editing problem on that thread for some reason).

[Savage]

Will do- remind me in a few days (there seems to be an editing problem on that thread for some reason).

Sorry about that. I'm just not a fan of unwarranted profiling of me on a public forum for absolutely no reason.

[rchavis]

Good read there .

[fishnfireman]

Sorry about that. I'm just not a fan of unwarranted profiling of me on a public forum for absolutely no reason.

Thought there was something missing.

[Savage]

Anyone that had to lift/remove the cowling on a EARLY model Optimax would understand my reasoning for asking about the weight difference of the Dynaliner foam compared to the stock configuration. Those Early model cowlings needed three men, and a boy to remove them. The newer cowlings are really nice and light, so that is why I asked the weight question. I have experience using Dynamat, but not Dynaliner.

The decibel question is the engineer in me wanting to compare numbers, nothing more, nothing less. Flatsboys later explanation makes sense, and his skills as a scientist in audio, are greatly appreciated.

[flatsboy]

[QUOTE=Savage;7399975 Flatsboys later explanation makes sense, and his skills as a scientist in audio, are greatly appreciated.[/QUOTE]

That's funny right there!
But i appreciate the compliment.

[JJolley]

Definitely going on my gotta get done list, like a few others here the older I get the more I like comfort and quiet.

[Savage]

That's funny right there!
But i appreciate the compliment.