single engine exhaust modifications

[SUPERMAC]

Just curious if anyone has ever done, or knows someone, or has info on or about any exhaust modifications. i was curious about directing the floor from the side (towards pump) out the rear and making an adapter that put it down into the water. like on a surf boat.

also just cause im a fabricator and generally have to tinker with anything i own, ive been wondering about exhaust mods in general. anyone added an actual muffler by chance to lower the drone noise. i know there isnt any HP to be gained by messing with the exhaust, but just for noise reduction perhaps.

 

[JEKVK]

Curious if you tried either of your ideas ? My 2021 SX190 has a 100DBA reading at cruise !

 

[SUPERMAC]

Sort of. I removed my resonator for a short while just to see what it sounded like. sounds like a low flying small aircraft on approach. lol wife didnt like it and made me put it back on. and ive been thinking of ways to direct the exhaust back down into the water, just not sure its worth it for my little boat. the piping that is back there seems like overkill and seems like a nice muffler of sorts would shush it down a good bit.

 

[JEKVK]

I have been working with Larry of Fresh Air Exhaust for the last 6 months . Hoping to have a product to install soon . It will be his first for a Yamaha.

 

[SUPERMAC]

Nice be sure to post it up. id like to see that.

 

[Jmorris195]

I pulled my resonator tank and shortened my exhaust tubing. 2500 to 3000 was stupid loud. Pulled the muffler to wrap it and I think I found a main source of noise. The muffler was sitting on bare fiberglass. Wrapped the muffler and added some sound dampening foam the the rear bilge and engine compartment walls. I will see tommorow if I have made a difference.

 

[zipper]

This guy has done exhaust mods. on a twin. No down pipe but his work is impressive.
Mention of the exhaust is in both threads.

https://jetboaters.net/threads/gmtech-custom-fishing-rod-holding-tubes.16169/page-2#post-281180

https://jetboaters.net/threads/results-of-latest-gmtech-mods-and-a-shark-on-the-boat.16388/page-2#post-281722

 

[Farny]

How is progress coming on your mods?

 

[2kwik4u]

How is progress coming on your mods?

Tag someone to get their attention if you're not quoting them

@SUPERMAC I too am interested. I had forgotten all about this thread.

 

[JEKVK]

Recap - original DBA readings with phone app and phone mounted on dash receptacle was 80 DBA at idle and 100DBA at any speed .
First effort was massive amount of sound deadening material installed in engine and exhaust compartments . Result - zero change.
Second effort was Fresh Air Exhaust - Bottom line - slower boat , Spray issues for anyone you pull , zero change .
Third effort , removed Fresh Air Exhaust , installed Centek # 1050300 between water box and resonator with supporting brackets, result is 74DBA at idle and 92DBA at any speed . Centek told me I could expect a 10% reduction . Comfortable earplugs still contribute to a relaxing outing. Shocked that Yamaha can market something this loud.

 

[dan144k]

Idea: would water injection directly into the exhaust pipe or waterbox reduce the sound decibel?

 

[2kwik4u]

Idea: would water injection directly into the exhaust pipe or waterbox reduce the sound decibel?

I doubt it.

Most of the sound is likely coming in the form of reverb out of the thin and light hull and fiberglass. High rpm vibrations are not well damped by lightweight materials and large open sections. Mass and smaller spaces will lead to squelching that sound. I suspect a better set of motor mounts will likely have the largest impact.

 

[tsledford31]

I pulled my resonator tank and shortened my exhaust tubing. 2500 to 3000 was stupid loud. Pulled the muffler to wrap it and I think I found a main source of noise. The muffler was sitting on bare fiberglass. Wrapped the muffler and added some sound dampening foam the the rear bilge and engine compartment walls. I will see tommorow if I have made a difference.

View attachment 158637View attachment 158638

Do you have a link for the muffler wrap you used?

 

[Cobra Jet Steering LLC]

I plan on doing 2 wraps since noise comes from 2 different locations and yes 1 is the muffler , just go to 5 and below get some yoga matts very strong and inexpensive then get some good contact cement.

 

[OurCrew]

I plan on doing 2 wraps since noise comes from 2 different locations and yes 1 is the muffler , just go to 5 and below get some yoga matts very strong and inexpensive then get some good contact cement.

What are the two locations exactly ?
Where are you cementing the yoga mates?

 

[Jmorris195]

Do you have a link for the muffler wrap you used?

Here is what I used.

https://www.summitracing.com/parts/tcx-hfn2-00bk25

 

[tsledford31]

I plan on doing 2 wraps since noise comes from 2 different locations and yes 1 is the muffler , just go to 5 and below get some yoga matts very strong and inexpensive then get some good contact cement.

Where are the 2 locations you are referencing? And is putting the mats on with contact cement a good idea? Or would metal zip ties do the trick?

 

[Whiskey74]

I was hoping Rivaracing would come up with something for the Yamaha boats like this for the PWC's. https://rivaracing.com/riva-yamaha-rear-exhaust-kit-2012-18-fx-ry15070.html