Poor mans exhaust silencer. Note the 10" rubber elbow. Clamped on and the suspension bracket from the platform is also bolted to the 10" tube further capturing the elbow. Holes in the side are for idle pressure relief. Rev 1 without the holes sprayed water everywhere. Now just a little spray out those holes. Next time I'll know not to drill holes to the outside and keep the docks dry. The downward part of the 90 I cut off. You can just see a little leading lip and the back edge about 1 inch higher like a bow thruster tube brow. Does a great job reducing noise and the 1000/1100 rpm howell. At speed, the elbows are out of the water just deflecting the noise down toward the water. No back pressure. At low speed, they just blub blub and we can talk in the back of the boat and to/from the dock. Exhaust rubber, nothing sticks to them but some grass. I was looking for 10" pvc to experiment with but found these at a surplus shop. If your exhaust is smaller, say 5 or 6", give that PCV idea a try and experiment before you plunge into the rubber exhaust part$. Factory 10" exhaust tube came out to swim platform back edge. The back edge of the swim platform had 35 years of abuse, Rebuilt it and added another 18" to boot. So this is a twofer, exhaust and bigger deck project.