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Can any mufflers pass 90 decibels ?

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Old 07-29-2006, 11:11 PM
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Default Can any mufflers pass 90 decibels ?

They are really crackin down here in Lake George.
I bought a decibel meter and have been testing
freinds boats. If the engine has any H.P at all
the are all coming in at around 94-95 Decibels.
So far one had CMI units,another had Hardin Marine
Units. My 35 EX with 496 ho's comes in at 89.7
with the silent choice turned on! I calibrated my
meter with a LGPC cop when he was testing my boat
and both of ours read exactly the same.
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Old 07-30-2006, 09:15 AM
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Default Re: Can any mufflers pass 90 decibels ?

What standards does New York use for testing? I am surprised you were at the threshold of 90 db with your captains call on. SAE J2005 test is specific as to the conditions and distances of testing procedures. The only mufflers I have heard passed did so with water injection into the mufflers also. Do you have water or run dry? One friend here in West MI has Borla's on his Cig. It passes now and he runs dry. I do know we need to do more. They keep modifying the laws to make things more restrictive here also. I know both my old boats pass SAE J2005 but neither will pass SAE J34 which is currently being proposed. The new one won't pass either law! Let me know what you find out on the law.
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Old 07-30-2006, 09:43 AM
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Default Re: Can any mufflers pass 90 decibels ?

The test is 1 meter off the transom. I believe in my case there
is some leakage thru the hull even with the silent choice
turned on. It is still kinda of lumping sounding even when on.
Also its a Fountian. I think the platform tend to amplify the low
tones. Its 90 decibels on the "A" scale,wind under 12 mph,
with the meter set on slow response.
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Old 07-30-2006, 10:08 AM
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Default Re: Can any mufflers pass 90 decibels ?

Rick,

I think we need to test run a set of CMI sound elimination mufflers. I have had a few people tell me they are the best noise reduction with no back pressure issues.Maybe we can get them to send up a trial pair for people to try and have tested while on the water.My mufflers are slip on,so at the next meeting I can let people try them to see if there boat can pass with them as well as other brands that maybe other members can bring with them.Let me know what your thoughts are.


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Old 07-30-2006, 10:17 AM
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Default Re: Can any mufflers pass 90 decibels ?

I put livorsi/northstars on a pair of 540's, they will pass the test, work the same as the cmi's.
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Old 07-30-2006, 10:50 AM
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Default Re: Can any mufflers pass 90 decibels ?

I was tested at 68db w/o mufflers !!
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Old 07-30-2006, 10:50 AM
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Default Re: Can any mufflers pass 90 decibels ?

or should I say ..... muffler
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Old 07-30-2006, 11:13 AM
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Default Re: Can any mufflers pass 90 decibels ?

I tested a Formula with Silent Thunder, single engine. It was between 89 and 90, with the drain plugs IN. With the drain plug out it was 91-92

Test is 1 meter off the transom, and 1 meter off the water, so if you have exhaust that exit under a fiberglass swim platform, it "should" help. The way I read the SAE standard, is transom. If they have a boat with built in swim platform, and they use the back of the swim platform it lowers the db a lot. Just by moving back 1 foot, the boot I tested dropped to 85db.

I guess EVERY Hacker on LG, needs to get a noise ticket, becasue none of them can pass 90db
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Old 07-30-2006, 11:15 AM
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Default Re: Can any mufflers pass 90 decibels ?

Not with 1100's
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Old 07-30-2006, 11:32 AM
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Default Re: Can any mufflers pass 90 decibels ?

Here is most of SAE J2500 testing procedures. It actually doesn't say transom, it says vertical projection. Does the NY law say SAE J2500 or 1 meter/1 meter? There is a huge difference when in court or testing under a strict set of rules set up by SAE Engineers.

Excerpt from SAE J2500
(copied and pasted from pdf)

4. Procedure

4.1 Measurement Site—A suitable site is a body of water free of large obstructions or reflective surfaces such as
buildings, boats other than those involved in this procedure, large embankments or breakwaters, etc. for a
minimum distance of 8 m (25 ft) from the boat being measured. The boat being tested shall either be moored
to a dock or lashed to another boat. If moored to a dock, the dock shall be of open construction so that it
presents a minimum of reflecting surfaces. If the measurement is made in open water, the boat being
evaluated shall be lashed to the measurement boat to prevent relative motion and to allow positioning of the
microphone in the prescribed location. The measurement boat shall be positioned to minimize reflected
sound.

4.2 Boat Operation—The engine shall be operated at low idle speed within the engine manufacturer's
recommended operating range, in neutral gear if so equipped. For motorboats without a neutral gear, the
engine shall be operated at its lowest operational speed. The engine shall be operated for a sufficient amount
of time to allow water to flow through the exhaust system before taking measurements.

4.3 Measurements

4.3.1 The microphone shall be placed at a distance of 1.2 to 1.5 m (4 to 5 ft) above the water and no closer than
1m (3.3 ft) from the vertical projection of any part of the boat in the area adjacent to the exhaust outlet(s).

4.3.2 The meter shall be set for slow response and the A-weighting network.

4.3.3 The observer reading the meter shall not be closer than arm's length from the microphone to minimize sound
reflections.

4.3.4 The applicable reading shall be the average sound level measured during a period when the background
sound level is at least 10 dB lower than the measured sound level. Background sound level includes wind effects, noise from boats other than the one being measured, wave action, boat wakes, and other extraneous
noises.
Peak readings of intermittent sound levels created by wave slaps or changes in sound level due to
wave action and/or engine speed variation shall not be included in the applicable reading.

4.3.5 The observer shall record the applicable reading and the background sound levels taken immediately before
and immediately after the applicable reading.

5. General Requirements

5.1 The measurements shall be conducted only by persons qualified by training to perform these measurements.

5.2 Proper use of all test instrumentation is essential to obtain valid measurements. Operating manuals or other
literature furnished by the instrument manufacturer should be consulted for both recommended operation of
the instrument, and precautions to be observed.

5.3 Proper acoustical calibration shall comprise the complete measurement system including extension cables,
etc. Field calibration shall be performed immediately before and after each test sequence.

5.4 A measurement shall be invalid if changes in the background sound level affect the applicable reading.

5.5 The use of the word "shall" in the procedure is to be understood to be mandatory, while the word "should" is to
be understood as advisory.

PREPARED BY THE SAE MARINE SOUND LEVEL SUBCOMMITTEE OF THE SAE MARINE TECHNICAL COMMITTEE AND THE SAE SPECIALIZED VEHICLE AND EQUIPMENT SOUND LEVEL COMMITTEE
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