exhaust sound level

[HyperDonzi]

i called corsa today about converting to thru hull exhaust and the total price is just under $460. 388 of that is the silencer tips. how loud do you think a 4.3 liter with 4" thru-hull is? im in ohio and the law states that when at idle the boat must be under 90decibels. do you think i will have it under 90 with regular tips?

[Greg K]

IMO, at idle you'll be under the 90 decibel limit wit the regular tips. I just completed mine a month ago and isn't that loud at idle with stock manifold and risers. It does have a nice sound though..

[MOP]

How are they taking a reading, I've heard some require 2000 rpm with the meter about 10 foot behind. That would be similar to the checks done on cars.

[HyperDonzi]

i believe at idle over the transom

[Rootsy]

in all honestly 90 dBA is not that loud when it comes to open exhaust, it can be sorta uncomfy on the ears though... someone hollaring is around 80 but the scale is logrithmic so a step to 90 is considerable. Sam Pilato told me his 16 read 89 dBA @ idle i believe in stock condition. his boat has 4 inch straight cut tips, stock merc exhaust and a 350...

hey if yu are on the edge... just have em check you on a very damp humid day wink

[HyperDonzi]

heres how they do it,
90db at idle 5feet back and 3 feet above the water.

[Last Tango]

For the curious, when sound is measured in decibels (dB), a 3dB increase is a doubling of the sound pressure (noise) or intensity. Correspondingly, a 3db drop is cutting the noise in half. The scale is non-linear, but is 20 times the common logarithm of the ratio of the pressure produced by the sound wave to a reference pressure.
If it sounds loud to you, it probably will not pass. The onset of pain and subsequent damage to the human ear is 90 dB which is why it is the reference point. Beyond 90dB damage occurs to the Cilia (little tiny hair-like structures in your ear that vibrate like tuning forks to stimulate the auditory nerve). These structures break when the noise level increases over the 90db range. They never reform. That is why folks who live and play around loud music, etc., seem to get used to the noise. They are growing deaf.

I love the sound of an open exhaust on a finely tuned V8 motor (any V8 race car). I also love the sound of a finely tuned V8 muffler system ('60's Pontiac GTO, new Corvette ZO6). The most compliments I get on my C18 are its sound - EMI Thunder exhaust system through Corsa muffled tips. Looks good, sounds good, makes the passengers happy and the lookers jealous. I have Quick 'n' Quiet on my Z3250 w/twin 454 Mag MPI's. In the Quiet mode it is impressively throaty. In the Quick mode, I gain about 3/4 mph (GPS) and lots of unhappy looks from my passengers.
Loud is not necessarily fast - attest all the noisy 4-cyl rice-bunner cars running around these days with Turbo tips. Do you really LIKE that sound? Unfortunately it is the same with 6 cyl motors (My '01 Porsche 996 GT racer sounds nasty with open exhausts and headers, and sweet with the factory Cup exhaust which runs a muffler. There is little measureable difference in the two set-ups in terms of speed. Mazda rotory engines are the worst in terms of nasty noise when run with open exhausts).

Unless you really are racing your boat, think more clearly about what SOUNDS good and what sounds LOUD.

[smokediver]

jkeefe sent me a little video with sound on his 4.3 ask him to send it to you .

[HyperDonzi]

last tango, what would you reccomend for a deep, throaty exhaust?
the corsa people reccomend:
2 18"x4" hoses $120(+/-)
8 clamps 12$
tips silenced 388

[David O]

For information on noise levels requirements per state see.
USCG Boating (http://www.uscgboating.org/reg/referenceguide/reference.html)

[McGary911]

David O, thanks for the CG link. Something funny tho...From that doc:
Twenty nine states have a maximum noise level for motor boats, 27 do not.

29+27=56 states? :confused: Granted, I was away in the Cayman's for a week, but I didn't think things changed this much....Beats me why there would be any confusion on this issue...