Originally Posted by Ghostrider

Remember: Loud Boats Save Lives!

Originally Posted by jeffswav

Good risers should have a 4" outer diameter with at least a 3.5" inner diameter. The water travels through the exhaust and keeps it cool then exits at the end. The riser fits on top of the manifold. Take a look at some manufactures websites. Eddie Marine, Imco, Stainless Marine, maybe that will help.

Originally Posted by Ghostrider

Risers are a combination of height and diameter. The best sort would be the high rising long tail length ones as they would have the highest flowing bend and the latest mixing exhaust and water, but they don't always fit under your hatch (as I found out the hard way), the next best ones would be the low rising bend with the long tail pipe which still has a smooth bend with less rise and the long tail pipe helps stop the water getting back up the exhaust passage and into the heads as it mixes further away.

Heres some pics: (the green ones are cast aftermarket EMI Risers, don't laugh, I think they look great! )

Originally Posted by ittledoo

So I would assume the long risers, where the water introduces right at the end of the riser, increases the decibel level by 10db +/-3??

Originally Posted by NoWake200

Could it be that there is less back pressure... smoother exhaust flow of the aftermarket header creating the increased db.

Just my thought.... probably wrong.

Originally Posted by ittledoo

Well, I thought that the purpose of mixing the exhaust w/ the water is what muffles the noise. So if there is less muffled, inverse on the noise.

The only reason I bring up that issue is there seems to be more and more lakes going to a db level rule.