Exhaust Turn Downs
 

I need to do something about the decibels on my Outerlimits SV43. I'm looking at installing Gibson turn downs, any cautions or suggestions? Thanks

Got any old mercruiser elbows around? Couple hunk of four inch hose and fake it. See what it is like before buying the shiny version. If you have to add length to get it below waterline, the oval merc hose is a wierd size. Not 4 inch.

I have a set of crappy ones that you could borrow and tryout, I made them up to see if I liked them or not. turns out I didn't. The spray from the water and air is aggravating. they are 4"

P.M. and we could work something out.

Have you looked into the GGB inserts?

GGB Exhaust Technologies Marine

They are strict about noise where we boat and the CMI Sound Eliminators I had were still too loud at idle. I installed the Gibson downturns five years ago and haven't had any issues.

GF?

I love my GGB inserts. They take about 6 dB off at idle and do not restrict rpm unlike some other inserts I've tried. 6 dB may not be enough for your but that was my experience from direct measurement.

The turn downs will work but turn down depth is important. They will splash a lot if not set deep enough. I made a test set out of 4" ABS drain pipe for concept evaluation.

How long were the GGB's that you saw 6db reduction? Were they the sport or competition version?

4" diameter, competition and I believe 4 or 5 rings long. Competition has a slightly bigger inner diameter.

GK
The law in Wisconsin is 86db. Nothing will pass with your engines but turn downs will be the closest.

I believe they make the inserts with up to 15-20 discs. That will REALLY quiet it down. I bought the 5 disc non competition inserts for my 496 (I know it's not that loud compared to other engines). They were too quiet. I cut 2 discs off. With 3 discs at cruise it is just as quiet as with the Corsa quiet exhaust on with no lose in speed. I was going to weld a bracket on the 2 discs I cut off and see how I liked the 2 disc setup, but haven't yet.