outlw36

I have 575sci motors and looking to lower the decibals as most lakes my way now have a sound ordinance. Looking for something good that will last.

weekend@burnies

Gibson turn downs , if that's not enough Aqua power clamp-ons with Gibson turn downs worked here in MN

ThisIsLivin

I have Gibson clamp on mufflers, I was concerned that turn downs would suck to much moisture on the long river cruises. I also hear that GGB is very good as well. The Gibsons take the bite out and still leave you with a nice rumble.

Bawana

CMI sound eliminations are the only mufflers I will use. They can be rebuilt, adjusted, and are the only mufflers that will get you down in db's to make you legal, and most importantly not cost you mph.
Its not rocket science, to reduce db's in the marine application ( with the length we have to work with) you have to make restrictions in the exhaust to lower db's thus increasing back pressure,thus loss of HP.
The sound elimination was designed to circumvent the noise laws: whereas, by law in most states you can't USE silent choice mufflers to reduce noise. They have to pass db's open & closed.... The CMI's do just that, but you don't control it at the helm.. The mufflers do it automatically. They make them in different size cans 5 & 6" I have used the 6" in blower motors of over 1000hp , would only use the 5" on 500hp or less.

pstorti

iTrader: (2)

I tried Imco clamp ons they were to loud and then the Gibsons and the were much better and even sounded better.

SkiDoc

iTrader: (4)

Hotboat idid a pretty well designed test of mufflers some years ago. They measured noise reduction and loss of power. I will see if I can dig it up and post it. Although all set ups are different, it gave some pretty decent info. Zoomers were the winner. I know clearly the down turns were not in existence at that time.

502ss

iTrader: (3)

I shot a couple videos of the cmi sound elimination both with and without! I saw 108db without and 84db with

http://youtu.be/Xy-7UolI1No

http://youtu.be/ZX0sVVShGc4

Bawana

Very nice.. In the second video I would just like to point out you have the mufflers installed upside down. I hope when you put them on the boat you have them turned 180*.... reason being there are three guides inside & one has to be placed at the 6 o'clock position; the way you have it now they could bind and not slide open & closed they way they are designed to.

502ss

iTrader: (3)

Thanks for the feedback. As you can in the video the clamps are at the 9 o'clock position (looking at the back of the engine) simply for ease of install for this test. When the mufflers were installed on the boat the clamps were installed at the 6 o'clock position with the logo's pointing up as designed. Agreed this is a different position then seen in the video but not 180 degrees.

I have since switched to a different muffler so either way it's no longer a concern!

Tibbstoy2

iTrader: (1)

I ran the 6" Clamp-on CMI Sound Elimination Mufflers for 3 years. I had 4.5" exhaust where the tails let water into the stream at the tip - so basically the muffler was fully wet. They did get my boat down to 90 dB on one engine, 93 dB with both idling. Naturally aspirated 540's - 700hp. Michigan law is 90 dB, so if the officer asked me to start both, I was toast. They did work pretty well.

The issue I had with them was a design problem... To Bawana's point, they are technically rebuildable, but the 3 shoulder bolts that the outer spring loaded assembly traveled on ride on a single wall thickness inner stainless tube that starts out as a slot and slowly enlarges year by year. By the 3rd year (150 hours of use), I felt like I needed to replace them because the slots almost doubled in size. As long as CMI carries the main outer ring assembly, then I suppose that's OK. The only issue is that's probably half of the muffler... so it will be expensive.

I personally like the pneumatic diverter style that Teague or CMI sells better (not legal in every state). I ended up making my own pneumatic system and built rebuildable tips with pins that rode on Bronze bushings to keep things tight. Been great for 4 years now, no signs of wear.