Before you bash, I have read the other threads and still can't decide which way to go. I have blown 540's with 4.5" dry stacks (EMI's) that are too loud in some areas that I boat so I need to do something about the noise. Doesn't have to be full time but I need something at idle. I don't need a Cadillac but even going to eat attracts the wrong attention. Yes, I know I'm getting old.

I've looked at the options for some time & need some input. Keep in mind that I have a 38 Fountain. The exhaust at idle is just above the water line.

Here's my take on the options.

Turn downs - I have read about reversion issues with turn downs but that enlarging the relief hole may help. If I went this way, the relief hole will be underwater on the Fountain. Any thoughts about relocating it & enlarging? I think it might work.

GGB - I have heard a lot of good things but they haven't returned my calls I've resorted to emailing them - we'll see.

Slip-on/transom mounted cans would be underwater at idle due to the angle of the exhaust at idle. I'm not sure that this would make a difference or create a potential reversion issue as there is no relief hole unless I drill the can.

Are there any 4.5 slip-ins that are worth looking at? I doubt that with dry stacks they would be very effective. Almost everything I have found is 4".

I would consider other options - toss them out & thanks for the help.