Mufflers or Turn Downs

NEVERSATISFIED · 07-06-2008, 12:38 AM

Would like to tone down the boat since patrol is cracking down on noise. Any pro's or con's to mufflers vs. turn downs? Like turn downs but concerned with turn down's forcing water back into exhaust from waves slapping transom while swimming at the beach.

Thanks Steve

glen george · 07-06-2008, 04:43 AM

I had the gibson turn downs, looks cool, good ideal design, but i went back to my IMCO mufflers , better all aroung soung reduction = looks,

Elite Marine · 07-06-2008, 08:51 AM

We can get you the CMI Sound Elimination Mufflers for
$ 995.00 in the 4" x 5" clamp on style or we can get you custom turn downs.

You will not draw water up into the engine, its a 4" column of water, there is no engine made that can produce that type of vacuum.

Ratickle · 07-06-2008, 09:46 AM

This is a question that currently has no answer in my opinion. The edited Ohio law is posted below. Around here they are starting to test the boats often. J1970 would be exceeding 75db from shore or a stationary object such as an anchored boat or dock. I think on higher HP applications there is no perfect answer. What is needed is a muffler system that has no major increase in back pressure at WOT, muffles to 75db at 75 feet at cruise, and is below 90db at idle at 3 feet.

I might try leaving on my Corsa Captains Call and adding CMI sound elimination in place of my current tips. I think that will work for 750HP but not exactly positive. If J34 passes in Michigan as they are trying, that won't work either. Would have to have permanent mufflers on that worked at WOT which the CMI's don't.

OHIO LAW

Exhaust Muffler Required: Effective January 1, 2000
Every powercraft operated on the waters in this state shall be equipped at all times with a muffler or a muffler system that is in good working order, in constant operation, and effectively installed to prevent excessive or unusual noise.

No person shall operate or give permission for the operation of a powercraft on the waters in this state in such a manner as to exceed a noise level of 90 decibels on the "A" scale when subjected to a stationary sound level test as prescribed by SAE J2005.

No person shall operate a powercraft on the waters in this state in such a manner as to exceed a noise level of 75 decibels on the "A" scale as specified by SAE J1970. Measurement of a noise level of not more than 75 decibels on the "A" scale of a powercraft in operation does not preclude the conducting of a stationary sound level test as prescribed by SAE J2005.

No person shall operate or give permission for the operation of a powercraft on the waters in this state that is equipped with an altered muffler or muffler cutout, or operate or give permission for the operation of a powercraft on the waters in this state in any manner that bypassed or otherwise reduces or eliminates the effectiveness of any muffler or muffler system installed in accordance with section, unless the applicable mechanism has been permanently disconnected or made inoperable.

No person shall remove, alter, or otherwise modify in any way a muffler or muffler system in a manner that will prevent it from being operated in accordance with this section.

No person shall manufacture, sell or offer for sale a powercraft that is not equipped with a muffler or muffler system that prevents noise levels in excess of those established in division (B) (1) of this section.

RBeyer · 07-06-2008, 11:09 AM

I am running a Procharged and modified 454, 720 HP. I installed Zoomers short barrel mufflers this year for the reasons you are concened. Great sound and nobody even looks at me, I see no power loss in fact maybe a little gain. $699 for thru hull.

Ratickle · 07-06-2008, 11:32 AM

Quote:

Originally Posted by RBeyer

I am running a Procharged and modified 454, 720 HP. I installed Zoomers short barrel mufflers this year for the reasons you are concened. Great sound and nobody even looks at me, I see no power loss in fact maybe a little gain. $699 for thru hull.

Has anyone run a test on your boat for dba? Also, when you say great sound, at WOT it still sounds like you have something under the hatch?

BGIII · 07-06-2008, 08:47 PM

I added mufflers to my boat this year and I love it. We can actually talk while flying down the lake, I can hear the engines instead of the exhaust and I feel like I have done my part to keep the noise levels reasonable. If you don't have silent choice, I think mufflers with turndowns would be the cats azz.

Ratickle · 07-07-2008, 08:09 AM

Quote:

Originally Posted by BGIII

I added mufflers to my boat this year and I love it. We can actually talk while flying down the lake, I can hear the engines instead of the exhaust and I feel like I have done my part to keep the noise levels reasonable. If you don't have silent choice, I think mufflers with turndowns would be the cats azz.

Which mufflers and how much HP are you running? Any less power and have you been checked? A semi-loud muffler with a turndown might be the best. Will look into that.

BGIII · 07-07-2008, 08:43 AM

Quote:

Originally Posted by Ratickle

Which mufflers and how much HP are you running? Any less power and have you been checked? A semi-loud muffler with a turndown might be the best. Will look into that.

I bought some new take-off Corsa's that came off a Formula 382 w/ 525's and I have power similar to an 500EFI. I also removed the last baffle that is riveted in, it looked like the biggest restriction point of the muffler and is easy to replace if I have a problem with the law. I have never been checked so I have no idea what my idle db was or is but it is a whole lot quieter than before. I cannot see any difference in speed versus without but I have not used a scientific method to prove that. I asked Corsa if they would be okay into the low 600 horsepower range and they told me these would be fine. I was full of gas and people and crap this weekend and it ran within 1-2 mph of the best it ever has. I still cannot believe how much more enjoyable the ride is with the mufflers on, I will never be without again.

RMPRam · 07-07-2008, 01:06 PM

Here is how I "solved" that problem. The exhaust pipes are 4-5" under water @ idle, thus killing most of the "noise" and all 4 are between the drives and pointing downward , sending the exhaust rearward, not out to the side. I have not done a db test on this system, but I know it is a lot quieter than when I had Gaffrig air-mufflers, with built in turndowns, that leaked ex. around the butterfly's. The motors are 572" PSI supercharged, 1100hp. Hope this helps.