I have run them and IMO they sound great. They take away the high pitch sound but probably not going to pass sound police. Can't beat the price either.

Thanks

Here is side by side idle. My 33 is stock 502 mag mpi's. Charles Scarab is 500 HP's, CMI headers with GGB inserts.

EDIT: Yes he passes sound police no problem and I got a ticket later that day

From my research the GGB are the best for reducing noise and also they are cheap.But you need to be careful because they are tapered and you have to order a insert that is a little smaller than your pipe at least this is what I have heard

I ordered the 4" for my 4" pipes. They fit with no issues. No taper to them.

Do you know which inserts he is using?

Is any additional tuning required on a carb motor?

I had the 4”x5.5” units and they worked great. If you have the space I’d recommend getting the longer ones and cutting rings off until you get the sound you like.

Tried to send a PM but the box is full!

Shot in the dark here and an early morning wish
Do you have any for sale? or know of any?
Looking for 4" Dia and do not care what lenght.

I run dry exhaust, so my only option was the GGB Inserts. I run the exact inserts you are looking at and the sound difference is HUGE! The first video is of my boat without any muffler and the second is of it with the mufflers. They really took the crackle out of it and dropped the sound level quite a bit. I do notice a little bit of speed loss, but only 1-2mph and I don't run them all the time, pretty much only when the whole family is going to be on the boat.