I will probably get flamed for this but my boat is a cruiser and we spend lots of time just cruising the intercoastal at slow speeds between ocean runs..... did a recent repower to Merc 496 EFIs and they are super loud. Adding in-line mufflers helped a bit but now thinking I need downtube or something under the dive platform. Flappers are about 9-inches above the water.

Anyone have ideas?

Thanks

Swampy

The turn downs are really only meant to be in the water at idle or close idle speeds

Get rid of the through hulls and go through the prop via the y-pipe. 496's run fine that way.

I have arneson drives so will need some sort of J-pipe outside the transome. I re-measure now that boat is in the water - the bottom edge of the flapper is at water level so I wont need much.

Once on-plane I dont care how loud she is

Swampy

Any of the major marine OEM's carry down turn pipes. Gibson, Corsa, Hardin.

A friend made some up out of PVC to test dimensions. They actually worked fine for a month while the SS steel ones were being made.

nice - I will try that. How much under water would you Folks recommend I try?