Noise Level !

[Sam]

Well I splashed my sisxteen today for the first time since the instalation of a new Stainless Marine exhaust system. Based on the noise level I heard a few weeks ago while running it on the muffs I knew it was louder than the stock stuff. So I picked up a dB meter at Radio Shack so I could see what the real story was. At approx 3 ft from the transom I get a reading of 93 to 94 dB. I say 3ft because that's how the water cops measure noise levels here. If I'm not mistaken the max dB level here in Mich is 90dB @3ft. Fourtunately the body of water where I run most of the time is infested with loud offshore types. For the most part the cops leave you alone unless your in a congested area and then maybe they might write you up. At any rate it sounds great and I know I dumped over 100lbs of dead weight by making the switch.

Sam :D

[Rootsy]

we need to check my exhaust sam... doesn;t sound quite as loud as yours but you never know.. you have to speak up to talk to someone when standing behind it... :D

[Digger]

SOUNDS great Sam! Could you bring that decibel meter to AOTH with you?

[boldts]

Food for Thought... I know the last thing you all probably want to do is place any kind of muffler on your thru-hull, but I've been told that the Shot-Gun mufflers work exceptionally well. I've also been told that because they have internal flaps that remain closed until the exhaust pressure rises, that they increase the bottom-end torque of the engine. In some cases the engine performance is increased so much, that the prop will blow out if the throttle is nailed from a dead stop. Not sure if that is an advantage or not, but these mufflers are supposed to increase fuel efficiency and of course lower the exhaust noise enough to pass the current laws. This includes the BB engines running performance exhaust systems.

Scott
Not making enough noise yet to have to worry :)

[clayman]

How about throwing the grandfather clause at them? "this is the exhaust that came on the boat new 20 years ago! officer." at what rpm do they check it at? From what I have read in powerboat mag, those laws are pretty much un-inforcable. There are to many varibles for the testing. They have the same problem with Harleys. What rpm?,what if you don't have a tach? how far from the tail pipe?, moving or stationary? what is the ambiant noise in the area, etc. If I ever got one, I would fight it.
Jim

[DonzigoJR]

Officer,
"This is a classic Donzi. What part of quite do you think I understand? How dare you tell me this is to loud. I was just thinking how quite this is compared to the rest of my friends on the registry.......Go ahead give me the ticket!!!" :confused: :mad: :confused:

[Sam]

NO problem Digger you can be first.

Sam :cool:

[MOP]

Anyone on the board have Shot-Guns? And where can I look at them?

[Sam]

Check with Stix Magill, I think he bought a set from a friend of mine.

Sam

[farmer tx]

MOP
I think Rex Marine makes them.
I've had them on some over the transom
headers for 18 years ,just had them
rechromed 2 years ago. The new style
are stainless, so are much improved.
Seems they are about 400. each though.


Later,
Mark

[Ed Donnelly]

The shotguns are made by Drew Marine www.drewmarine.com (http://www.drewmarine.com) Ed

[MOP]

Got mail back from Stix, not a heck of alot of noise reduction and expensive, Capt Choice or the like much better! Thanks Sam for the lead wink

[boldts]

M.O.P. - Are you aloud to use Capt. Choice while being tested? Here in Ohio, I've been told to remove the name plate on the quiet switch so as to not bring attention to the option. I took this with a very large grain of salt. Those of us who have Capt. Choice know that when it is on, there is a flow of water that still exits the pipes. It's not like you can hide the fact that your using it. I have not been tested by the local water patrol, but I believe you have to run the engine with the pipes open.

Anyone check that 38 Scarab being offered by Drew marine? That deck is hot in more ways than one! :cool:

[MOP]

I have'nt even gotten to make holes in the back yet, may not! So far the Noise Police are not operating out by me. I think the laws are like everything else varied from state to state and probably Cop To Cop.

[Rootsy]

Jr.

Yes this is wet exhaust and yes it is very possible to be over 90 dBA.. Sam was 89 in stock form with stock merc center risers... i KNOW i am close if not slightly over.. just from gauging how loud you have to talk to hear anyone when standing behind it.. 80 dBA is basically like raising your voice...

Sam... you need to check her when it's raining out!

[MOP]

To bad Shot Gun don't make them without the holes so all the exhaust went through the drive at low speed.

[DonCig]

Is there any way to increase the sound level? I have the stock Merc. risers and unmuffled tips. Would the GLM manifolds increase the SPL? I have the silent choice on my boat and I use it, so having a louder exhaust at times is not as irresponsible at you might think, and besides, it is a Donzi.

Don

[RedDog]

Put a big block in and it'll sound better :cistineb:

[DonCig]

When this small block wears out, this boat will receive a Bill Mitchell 427 c.i. aluminum small block that will bark! But until then I am going to enjoy all the water time I can using this 300HP smallblock. It just needs to sound a little nastier.

Don

[Rootsy]

GLM aluminum, IMCO M-72 Stainless Risers, Corsa Straight Cut Tips (internal flappers)... 80 degrees, who knows on BP and a lot of humidity... ummm at idle.. 3 feet from transom between pipes... 104 dB C weighted Fast Response...

oh yeah JR... this is WET exhaust ;)

yes my 16 is kinda noisy and i like it that way :)

JR - holy at the moment

[MOP]

Just re read the whole post, I found out here in NY switchable exhaust is illegal, the two local water cops I spoke to said if you are not being an AH they don't bother ticketing. I did however find a neat little trick that does help just enough to be interesting. Water kept in the exhaust flow does cut the noise, problem is a goodly amount runs along the bottom of the hose doing nothing to dampen the noise. What a fellow I talked with did was to to cut 1/2" strips of S/S .050 about 2" long then bent them over sharply but still leaving a good upward angle leaning toward the tips he put three per side close together at the front end of his diverters which made the water kick back up into the exhaust flow. Also he noted his hoses to and tips ran a lot cooler to the touch, as we all know when using diverters most of the water goes down to the drive. His engine is a 540 carbed with tube headers I listened to it and it was quieter that it was last season. CDMA had brought up the point that water in the exhaust flow made a big difference. I am going to put the strips just before my tips as I have no diverters, I know some will argue "restriction" I don't think with 4" holes a few small strips will cause much.

Phil

[GEOO]

Check the local law noise level and type of reading. I think it's A or C rating ?? and fast or slow response?? I have't play with my meter in a while. You'll get a couple of dbs diff. depending on the setting.
I run Shot-Guns for the past three years. I like them. They quiet her right down. :shocking:

[RickSE]

These muffler cans are behind my 500EFI and really quiet the boat down. Even seems quieter than my old 350 with straight wet pipes. They sure as heck don't seem to effect HP. My only complaint is that with the flaps they have a tendency to splash water up on the back deck of the boat.

[Ed Donnelly]

I have shot guns on the Criterion and they take the sharp bark out, but still leave the rumble...Ed

[smoothie]

I put a set of these in my BBC exhaust and didnt notice any change in speed,I can talk over em at idle and havent been stopped yet by the law,and I pass em everytime Im out.

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