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noise management for Suzuki DF50 on my 16' Cruiser
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DMcD



Joined: 21 Jul 2016
Posts: 20

State or Province: AL
C-Dory Year: 2007
C-Dory Model: 16 Cruiser
Photos: DMcD
PostPosted: Mon Sep 11, 2017 4:23 pm    Post subject: noise management for Suzuki DF50 on my 16' Cruiser Reply with quote

I would like to reduce the noise at cruising speed on my 2007 Suzuki DF50.

Does anyone know if there is enough clearance under the cowl to add a layer of sound isolation panels?

measurement at cruise 88.4 dBA

octave bands:
63 Hz 89.1
125 Hz 93.9
250 Hz 92.0
500 Hz 87.0
1000 Hz 81.7
2000 Hz 71.5
4000 Hz 66.3
8000 Hz 61.9
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BrentB



Joined: 15 Jul 2006
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City/Region: Greenwood
State or Province: IN
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PostPosted: Mon Sep 11, 2017 4:28 pm    Post subject: Reply with quote

wow
neat, data set

What instrument are you using and distance from OB.

Our Industrial Engineer moved to another office location and miss our discussions

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DMcD



Joined: 21 Jul 2016
Posts: 20

State or Province: AL
C-Dory Year: 2007
C-Dory Model: 16 Cruiser
Photos: DMcD
PostPosted: Mon Sep 11, 2017 4:32 pm    Post subject: noise measurement Reply with quote

Its an industrial sound level meter I was able to borrow (B&K 2250). Measurement was taken at the approximate location of my head when sitting in the pilot seat.
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bobjarrard



Joined: 03 Oct 2010
Posts: 458
City/Region: Boulder City
State or Province: NV
PostPosted: Mon Sep 11, 2017 6:56 pm    Post subject: goals and cost Reply with quote

I have had to mitigate sound issues in the past. You can change the frequency or modify the volume. Some "octaves" are more bothersome than others, I have lost so much high frequency that I sometimes cannot understand a soft spoken woman or child but the bass beat from a low rider car drives me nuts.
Start with the motor attachment point and method, the stern is a type of amplifier. Make sure the motor itself has no controllable sound sources (leaky exhaust or intake whistle), then think sound insulation as marine approved lead sheeting. The Red Wing has an engine cover as in : http://www.woodenboatstore.com/product/plan_18_6_Redwing/powerboat_plans
and the Nimble Nomad has the same thing (most of them with a 45 or 50 HP Honda OB as in:
https://www.youtube.com/watch?v=_nSP-LIFh4Q
Hope this helps.
Bob Jarrard
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Aurelia



Joined: 21 Aug 2009
Posts: 2331
City/Region: Gig Harbor
State or Province: WA
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PostPosted: Mon Sep 11, 2017 7:13 pm    Post subject: Reply with quote

This is what I did with this product and it was very noticeable for us on a 75hp 202 Honda.

http://www.c-brats.com/modules.php?set_albumName=album2071&id=20140821_194231&op=modload&name=gallery&file=index&include=view_photo.php

This product,

http://www.hytechsales.com/prodsc.html

We then had a sound deadening panel sewn into our camper canvas between the motor and cockpit. Below the rear window shown here:

http://www.c-brats.com/modules.php?set_albumName=album2089&id=20140426_145801_resized&op=modload&name=gallery&file=index&include=view_photo.php

I think is was something like this,

https://www.summitracing.com/parts/the-14600?seid=srese1&cm_mmc=pla-google-_-shopping-_-srese1-_-thermo-tec&gclid=EAIaIQobChMI4cSL36Ge1gIVDC1pCh13bg_CEAQYByABEgK0ovD_BwE


Greg

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thataway



Joined: 02 Nov 2003
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City/Region: Pensacola
State or Province: FL
C-Dory Year: 2007
C-Dory Model: 25 Cruiser
Vessel Name: thataway
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PostPosted: Mon Sep 11, 2017 10:06 pm    Post subject: Reply with quote

Most modern outboards have been engineered to decrease the sound as much as possible. I cannot answer the question about clearance, but I would investigate it by putting some in-expensive soft foam on the inside of the motor and see if it contacts the metal frame of the outboard or flywheel. also one would have to be careful to allow adequate air flow to the intake, and to cool the charging mechanism--which is basically part of the flywheel. You can put some graphite (Key lock spray) on the metal to see where the contacts of the foam are, and then cut down the foam to be sure and clear.

"Sound Down" makes a foam, leaded vinyl/ foam material
Product brochure here Makes a number of products to decrease noise pollution in boats. Basically it is foam, vinyl impregnated with lead and then thinner layer of foam. I have used it to line boxes, which I have put over inboard engines or generators. There is also a carpet underlay material, which is as thin as 5/16" thick. It has the vinyl lead and one side of foam, but if clearance is an issue, I would suspect that you can glue at least the 5/16" material inside of the cowl over the entire structure--and then use the thicker pieces where you can. Before that was available, i used lead sheets, glued or nailed to plywood, and then covered with foam.

Also is there much vibration being transmitted to the hull of the boat, which is resonating. Is the glass in the splash well or any other thin layers of glass adding to the noise by resonation?

Also decoupling the vibration from the transom can help. There are pads made which go under the outboard, and then the motor re-bolted in place--that might also help to de-copule the engine vibration from the hull.

Also it i possible to put one of the bore scope type of cameras either snaked under the cowl or thru the air intake to visualize how much room there is for insertion of foam.

Of course there is always the opposite way, of wearing either noise canceling headphones, or hearing protection as used on the range.

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Thataway
Thataway (Ex Seaweed) 2007 25 C Dory May 2018 to Oct. 2021
Thisaway 2006 22' CDory November 2011 to May 2018
Caracal 18 140 Suzuki 2007 to present
Thataway TomCat 255 150 Suzukis June 2006 thru August 2011
C Pelican; 1992, 22 Cruiser, 2002 thru 2006
Frequent Sea; 2003 C D 25, 2007 thru 2009
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Home port: Pensacola FL
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BrentB



Joined: 15 Jul 2006
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City/Region: Greenwood
State or Province: IN
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PostPosted: Mon Sep 11, 2017 10:25 pm    Post subject: Reply with quote

Probably a stupid question

How many mounting bolts and are they torqued to specs?

fyi
Rigging guide
http://www.mdmotors.ru/netcat_files/216/180/SUZUKI__DF25___DF250_Instruktsiya_po_ustanovke_motorov_1.pdf
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Forty Two



Joined: 16 Nov 2004
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PostPosted: Tue Sep 12, 2017 9:06 am    Post subject: Reply with quote

Our 17 ft Arima had a table mounted over the outboard (standard Arima hardware). Outboard sound level was much less when running with the table in place. Could something like that work for you?
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DMcD



Joined: 21 Jul 2016
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State or Province: AL
C-Dory Year: 2007
C-Dory Model: 16 Cruiser
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PostPosted: Tue Sep 12, 2017 9:41 am    Post subject: thanks Reply with quote

thanks for the great ideas and info. It's a lot to absorb (no pun intended).

I don't know for a fact that the mount is to spec, I made the assumption that it was.
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hardee



Joined: 30 Oct 2006
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PostPosted: Tue Sep 12, 2017 10:11 am    Post subject: Reply with quote



Note the foam wrap on the OB here. This was on a stretched 16 that OldGrowth Dave did. He ran it up to Sequim from Olympia. Said the foam cover did help with some attenuation.

Harvey
SleepyC Moon


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BrentB



Joined: 15 Jul 2006
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PostPosted: Tue Sep 12, 2017 10:22 am    Post subject: Reply with quote

When you remove the cowling hood top cover, is the gasket intact?
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spuncopper



Joined: 02 Sep 2012
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City/Region: Camden/ Lake Wateree
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C-Dory Model: 16 Cruiser
Vessel Name: Sock Monkey
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PostPosted: Tue Sep 12, 2017 12:12 pm    Post subject: Noisy Suzuki DF 50 Reply with quote

Hey DMcD,

I, too, have a 2007 16 Cruiser with the 2007 Suzuki DF 50. We have found the DF 50 to be quiet at slow speeds. However, up on plane the noise level bothers my wife; me, not so much... then again I have close to a total high frequency hearing loss.

I let my wife know when we're going up on plane and she puts foam ear plugs in her ears. She removes them when I come off plane. She keeps several sets in an old, plastic snap-cap prescription bottle. Works for us.

Take care and be safe, Spuncopper
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ssobol



Joined: 27 Oct 2012
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PostPosted: Tue Sep 12, 2017 12:16 pm    Post subject: Reply with quote

One thing to consider is whether the noise is coming from the engine or is induced resonance in the hull. On my boat there are certain RPMs where the noise is much more than others because of the resonance.
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BrentB



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PostPosted: Tue Sep 12, 2017 3:42 pm    Post subject: Reply with quote

Maybe you have a good boat guy in your area.

Are you close to Wefings? Why not call them for a curbside consult or take the boat to them.

I am not a specialist and often seek out a good people and companies to keep life simple.
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hardee



Joined: 30 Oct 2006
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PostPosted: Tue Sep 12, 2017 5:17 pm    Post subject: Reply with quote

I think the foam ear plugs are a good idea. Relatively inexpensive, easy to do and pretty effective, (based on foam earplug db losses in the 25 - 35 db range).

These are what I use on the bike since becoming convinced it was a good idea for hearing preservation. (It is not that the bike pipes are that loud, but that the wind, at speed, causes the increased db level.)

On my boat, the aft cabin door is closed when at planing speeds, so noise level is pretty low. (And about the time I bought the boat, there was a report showing that the Yamaha 40 outboards were quieter than anything else out there given the same power rating.) At slow cruise, I often have that door open, and the windows for good flow through ventilation, but at the slow speed, the OB's are running pretty quiet.

Harvey
SleepyC Moon

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