Which turn downs are you using and did the get your db under 90 ? Also what type of exhaust were they installed on? Wet, dry, size, hp of the motors?

I am trying to get the noise down on a pair of 1100's with cmi dry big tube headers. Need any good information anyone has.

1180HP NORTECH blower motors running thru cmi big tubes thru wet and out 6" tailpipes on 36 nortech cat, never could get it legal, nortech now has their underwater stealth exhaust works great, like a turndown only inside the motor compartment, on a v the turndowns I had made work awesome about 2-3 " below water line, yes you can hear blower whine at idle.

I know it's not a direct relation but should give some idea where yours may end up..

I'm running a 595hp 509 with Keith Eickerts and was 94db at idle WITH GGB mufflers....

I added a set of "downtubes" to the GGBs that sit 6" under water when at rest and now I'm at 83db at idle.....I'm not really a fan of the sound at idle but at least it's legal..


Here's a video in the water...
and a video out of the water ...


Doug

If it a side by side motor setup I would put the cmi turndowns on, GLH did this on his Tiger. If it's staggered the new cmi sound elim. should work, I have them on but have not run the boat since installing them.

More test results for you, 598 N/A, 750hp -
No mufflers: 112
GGB: 94
New CMI's: 94
Turn downs 7" under water: 86db

Rick