I currently have a set of Gibson clamp on's and I a totally happy with the Db level when cruising but I would really like it quieter when idling around the marina. I am thinking about adding a set of 90 degree turn downs long enough to be under water at idle but out of the water at speed.

I know that people have added the down turns but has anyone added them aft of Mufflers? They current mufflers are Gibson's with the double clamp and they are slid all the way forward (you cannot see the tail pipe because the the mufflers fully cover them) and they seem mounted very stoutly so it seems that there would not be an issue with it being strong enough to handle any forces that the water puts on them.

I know that a few boat part companies sell them, but it seems to me that I saw posts in the past talking about ones desgined for Diesel applactions that were half the price.

Anyone have any input to share? Or great idea's where to get some?

I had a set GGB had made for me to fit their mufflers..

In addition to the clamp they had a nut welded so you drill one hole in the muffler flange and install a bolt as a safety so you wouldn't loose the pipe if the clamp ever came loose...


NO issue with them.. Worked GREAT !

Boatally, thanks for replying...

It looks like that is exactly what I was talking about.

I assume that the concept worked and it greatly reduce the noise levels in slow water zones? Did pointing the exhaust down also reduce the noise levels full speed any as well?

What is the depth of the pipe in relation to the bottom of the boat?

Do you remember what the charged you? The $600 price tag at the performance boat supply shops seems over priced.

Anyone see any reason that I should not just weld them to my clamp on Gibson mufflers?

Don't recall how much they were.. I did get a deal on them from GGB since their mufflers didn't quiet my boat down enough to pass Wisconsin noise laws...


It was a bit quieter under way with the turn downs than without. Was a GREAT option for a noise Nazi state. Quiet at idle to pass their laws then came to life once on plane .. not a damn thing they could do about it.. lol

Use pvc and paint it same color as boat. Lol. Seen it before.

Me too.

I do believe that GGB will make a turn down WITH a muffler inside of it. $600 isn't bad for a turnkey solution with quality materials.

At least it matched the boat color! LOL!

I just saw a boat ad somewhere with PVC. I almost laughed out loud.

Now I'm trying visualize them painted green... Anyone one with photoshop?