Simple Low Cost DIY Outboard Exhaust Silencer/Muffler

[zmk1962]

There have been a few topics recently about outboard exhaust noise when flushing motors, neighbours complaints etc.

I have never had problems with my neighbours but was always conscious of cranking over my 200HP EFI two stroke, so I spent last weekend coming up with a simple DIY exhaust silencer/muffler.

Here are the results....once you see the youtube clip you'll get the idea and can adapt.

Hope this helps someone.

https://youtu.be/jpvsHWFFoWY

My 200HP now idles at flush at 80dB - which my iPhone app tells me is about nosie level of an Average Car.

Edited April 29, 2015 by zmk1962

[antonywardle]

That's great work.

I'd also started a system like that too and am now looking for an

Android app for measuring dB too

thanks for that

How does the water get out? Through the holes in the top under the cap?

How many holes do you need?

Edited April 29, 2015 by antonywardle

[locodave]

Pretty cool mate! I won't lodge anymore complaints now, I am in the hills too!

[zmk1962]

That's great work.

I'd also started a system like that too and am now looking for an

Android app for measuring dB too

thanks for that

How does the water get out? Through the holes in the top under the cap?

How many holes do you need?

The water mostly runs out from around the prop - my prop (Vengence) does nto have a solid core - some of the boating experts can comment but I think most through prop exhaust systems vent a bit to the front as well. From memory I read somewhere it helps with spinning up the prop from idle - so the water runs out through those cavities and around the prop edges near the front.

The muffler in the video was my second version. The first, had a longer pipe and no cap - it also worked with a deeper sound. I cut the pipe down when I could see where the water level had stabilised (as the water was running out from around the prop) and added a cap as it helped dampen the gasses now that the pipe was shorter.

There are 6, 12mm (1/2 inch) holes around the cap these are mainly to help vent the gasses - very little water comes out of them.

[zmk1962]

Pretty cool mate! I won't lodge anymore complaints now, I am in the hills too!

He he he ..... No complaints about the Hills !!! ...or from the Hills please !

[brad_tate]

Very clever, well done

Sent from my iPad using Tapatalk

[Nolongeramember]

Just putting it out there as another option and not to take away from zmk1962 as his idea is a nice one but I've found a simple round plastic garbage bin from any hardware store to be good for reducing noise also.

I fit it under the leg and raise the front of the trailer with the jockey to get the outboard leg as submerged as possible, then fill it with water. The flush and water flow is as good as your ever going to get and same with the noise. Its as quiet as being on the water..

I've fitted a tap to the bottom of the bin to make releasing the water easy when the flushing is done, and also a plastic clip to hold the hose from coming out.