An often overlooked benefit of propulsion efficiency and its reduced power demands is a quieter engine system. But as quiet as Wind Horse is under power, 57 dB at eleven knots, one of our goals for this haul out is to reduce the sound level further. Of course when you are at 57dB already, further reduction is not easy. The swim step extension will move the exhaust three feet /90cm further aft, and underwater, which will help – a lot. In addition, we are changing the exhaust system inside the engine room, hoping for major improvements here as well.

That’s a smiling Corey McMahon of Triton Marine in the photo above. Corey is sketching up what we have been discussing. If you study the photo, you will notice the dry exhaust riser is gone. It is unbolted, in pieces, on the shop floor. In its place is going a much shorter (but adequate) riser, this one three feet /90cm above the waterline rather than six/1.8m. The new position for the water injection elbow is shown by the spare hanging to the right of  Corey’s head. The brown cardboard tube represents an inline muffler, which we will step over to get to the outboard side of the engine.

We expect a 15 to 20 dB drop in exhaust noise within the engine room, substantially less heat radiation, and a reduction in exhaust noise transmitted through the structure by exhaust system support.

It will be interesting to see how much noise reduction we gain by all of this.