A large percentage of the propulsion noise on most engines comes from the exhaust system being in contact with the structure of the boat. This is a particularly difficult problem to solve on most designs. However, if you have an aft engine room achieving a favorable result is easier.

On the FPB 64 the exhaust system is totally isolated from contact with any structure. This starts

at the engine where the exhaust riser is supported by structure tied to the engine. The two inch/50mm square tubing (painted white) which looks like an inverted V in the center of the photo starts this process.

Next in line is the horizontal aqualift muffler. This is isolated with super soft mounts.

Then comes an elbow, again isolated with a rubber mount. After the elbow there is a short run under the swim step to the exhaust shut off valve.