Quieter Silencer/Muffler/Water locker than stock?

[Tipsynippertoo]

Hi Guys,
I have a Hunter 356 2002yr Yanmar GM30 and get fed up with engine/exhaust noise when we have to motor for any period of time. The engine sound proofing I have re-worked with a heavier/superior material on the engine cover, but still get a lot of engine noise into the rear cabin and heads which I would like to address, probably with "foam in a can" injected under the floor of the heads & alongside the engine on the cabin side where I think it is coming from (I digress!)
Has anyone changed the Silencer/Muffler/Water locker for something better than the stock one?
I am considering the Vetus NLP 350 which is supposedly 10db quieter (than what?!)
Recommendations?
Suggestions?
All welcome,
Thanks
Neil

 

[Benny17441]

That is a tricky question as tolerance for noise is relative. If the old muffler has lost some of its sound deadening characteristics perhaps a new muffler with improved design might make a significant difference at least for some time. Understand that some of the sound travels through vibration of the boat's structural shell and partitions. Reducing and isolating vibration of the engine and running gear can go a long ways to reduce noise. Try taking a reading in decibels of the current sound so that you can have a base figure against which to measure any changes or upgrades.

 

[Mark Maulden]

You have a 35’ boat. You can do the best you can with sound deadning mtl on bulkheads etc and muffler. Mufflers are just a water collection device with some partitions. You are going to have engine noise. Leave the spray foam at the home improvement store. Expanding foams can cause physical damage. Any kind of foam can trap moisture and disintegrate. Make sure the engine and gear mounts are still within specs as they can transmit sound and vibration to the hull. If you still cannot stand the “noise”, then a different boat is needed...or ear protection...

 

[ice breaker]

I suspect that what you are hearing is intake noise. Most yanmars did not have intake silencers until about 2006ish. We had lots of base noise on our 2004 which made motoring very unpleasant. I was able to solve much of the problem with a 4 foot piece of soft vinyl hose attached to the intake port. It did not change performance at all and got rid of most of the base pulsing.

Do not use thin hard plastic as that will whistle.

 

[NYSail]

Check your engine mounts

 

[lillia28]

I used a centek waterlift and a vetus Gooseneck. The exhaust noise is minimal, but the diesel noise is not. There is a fair amount of intake noise, and a fair amount of vibration. Good article here: http://gerrmarine.com/Articles/NoiseControl.pdf
For what it is worth, the centek-gooseneck works really well for me in controlling exhaust noise, and is a good place to start, but it won't make the boat so quiet that the only thing you hear is the ticking of the clock, but you probably have a quartz clock anyway.