How to quiet noisy exhaust?

Kaluvik, nice work. You need to deal with the moisture problem evident in the third pic and I would not leave the bare plywood bulkhead in the first pic. Everything else I see looks to have been done by someone who cares (you).
What you did doesn't adress the intake noise they're talking of, tho.

 

Thanks Mark
Like I said...it may not be relivent....I just wanted to post something with a picture.
I'm anal about dry fitting everthing I do...that ply is now painted.

Mark...Homer...do I know you...spend any time around Fairbanks?

 

No. I've been there three times.

 

Yeahh......this and that:

seems not to be the same animal! I understand.

 

Well the 10cm length of hose stopped the subwoofer effect, but I suppose now that I've identified the cause of plenty of noise, its worthwhile trying to minimise it by experimenting with different lengths of hose and mufflers.

I was thinking that an automotive muffler on the intake might be effective for its passive noise cancelling, but it may restrict airflow too much. Any thoughts on that idea?

Barney

 

Easy to measure Barney.

Assuming you did´nt change anything and the boat is in running condition, you put the hose on and have a ride in calm waters. If there is no smoke, continue. Set the throttle fix and put the hose off. Any change in rpm ?
Remember the setting.
Now put the (cheap) Rover air filter on it and do the same run, same rpm, and get it off while running.
Watch for smoke while the filter is installed, it would be a sign of a choked inlet.

But you can have it easier.
When you are fine with 10cm of hose for a wide range of resonance, you need just another diameter of any length to get rid of almost all of the rest. A plain metal mesh "airfilter" (in fact they hold just mice, rags, and t- shirts out), wider than the inner diam. of your hose, does it.

The Rover "oil" air filter has the same effect, but I assume the inner diameter is smaller than your inlet. then forget it.
And if there is a 90° or worse change in the direction of airflow it is not the way to go. I do´nt have the data at hand, but I remember that a 90° knee is about 20% or more restriction in air flow!

The muffler idea is one you should quickly forget. Exhaust gas pressure has no problem to overcome resistance of some severe amount. The same resistance on the inlet chokes your engine to death.

Regards
Richard

 

...if I may go back to one of my past posts regarding the water setarator type mufflers that we use on gen sets.......how big an engine can they cope with, I have only used them on small engines (say 25hp)?

 

Lubs

Barney was asking for a muffler on the INTAKE !!

The separator types I have installed cope wit 100hp easily. Dunno if there are bigger sizes around, we do´nt use them anymore.

 

How big is the gen ? is it a turbo?

 

Gen? Who talks about a genny?

 

Brand --I guess your bid on the Landrover filter failed.

A land rover is a hardy vehicle and is in every rough terrain countries. They are meant to be the most reliable vehicle capable of things others would not dream of . There filters are built with similar enthusiasm. a huge oil bath, with an intake surrounding the approx 10inchX 14 filter. These filters were made to supply clean air to a 2 liter engine crossing the Sahara. The intake is approx 6 inch dia, you can get your hand in and wipe them out.

To listen to suggestions that it would restrict air flow to a 38 HP is-- well.

If your 10cm pipe shuts down noise to an acceptable level then its done.

The rubber absorbs the noise, if you used a metal pipe your would just move the source of the noise.

Im gonna take my air cleaner off my cars I might get a performance increase!!!!!!!!! I wonder why they fit these useless air clogging devices.

Google filter boxes for performance, or in a similar kinda way intake plenum chambers.

 

Read the word GEN

 

Well got the GEN.................from Lubbers post.

Air filters, dear Frosty, capable of keeping Sahara sand out of a 2 ltr. engine have a serious resistance! The same filter on a 1,5 ltr. marine Diesel is a nonsense. It restricts air intake period!

The rubber does nothing in resonance avoidance! The length of the hose is it.

 

Not my ball park! Oh boy.

Your thoughts on filters is Sunday afternoon boy racer mechanics.

 

Ok

I agree..................
senseless to teach the invalid.......