Is a silencer necessary?

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Barleycorn

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Had a rotton day yesterday, had the raw water impeller fail, and cooked my plastic Vetus muffler/silencer.
A new one is £400, but I was wondering how noisy the boat would be if I just replaced it with a bit of pipe. I don't think it would effect the engine's running as we have run a lot of turboed tractor / plant engines with no silencer, the turbo tends to silence them.
The engine is a Cummins B series 210 HP.
Anyone heard one running like this?
 
My 2 x Perkins M135 do not have any sort of silencer/muffler. Just 4M of Vetus exhaust hose. The resulting throaty thrum can be quite nice to listen to on start up etc but after 8 hours or so it can become rather less so.
There are other muffler/water lock systems available in the EU ,somewhat cheaper than Vetus, but very difficult to come across in UK due to lack of internet coverage/dealers..Have just purchased 2 x 75mm versions for my boat.
You need to be aware of back pressure problems but most engine manufacturers and exhaust system suppliers give lots of help in this area.
 
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Thanks for the replies. The centek is half the price of a vetus. Only thing is that my vetus has a flap in it to prevent water going back into the engine. As the turbo is right on top of the engine, well above the water line, as is the exhaust exit, is there any need for this?
I am tempted to get a length of pipe to try it and see how noisy it is.
 
Most of the marine engine and muffler outfits will have some spec sheets around that give you minimum exhaust to waterline dimensions.

https://www.perkins.com/cda/files/4479350/7/TPD1399E issue 7 web.pdf
Around page 13 from memory.
My water locks/mufflers are languishing in the shed,waiting for me to get up sufficent interest in fitting them.My only caveat is how much power we will lose,not exactly having a surfeit of the stuff at the moment.
 
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Barleycorn said:
Thanks for the replies. The centek is half the price of a vetus. Only thing is that my vetus has a flap in it to prevent water going back into the engine. As the turbo is right on top of the engine, well above the water line, as is the exhaust exit, is there any need for this?
I am tempted to get a length of pipe to try it and see how noisy it is.
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You have now set alarm bells ringing.

Can we know more about your complete system, if your exhaust is reliant on flap in the muffler to prevent water getting into the engine it does NOT meet Cummins installation guidelines plain and simple.

What is exactly height of your 'spill over point' i.e from highest part of your your injection elbow to loaded water line has to be a minimum of 12 inches, age old rule which has the habit of eluding people who install engines.

As to the Vetus muffler you are better off without it, every installation I have tested with this stuff there have always been issues with exhaust restriction. If you end needing a muffler Centek is 100% better quality in terms of material and design, price is not relevant in this vital area.
 
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Thanks Latestarrter, I am not near the boat, but I would think that I had well over a foot between the exhaust elbow and the waterline. I will have a measure up at the weekend.
The centek, being made of fibreglass, is far more heat resistant should this happen again. A plastic silencer does seem pretty daft. If I do need a flap centek do a separate one, and probably buying this and a silencer would be the same cost as the vetus.
 
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Silence please

Barleycorn said:
Had a rotton day yesterday, had the raw water impeller fail, and cooked my plastic Vetus muffler/silencer.
A new one is £400, but I was wondering how noisy the boat would be if I just replaced it with a bit of pipe. I don't think it would effect the engine's running as we have run a lot of turboed tractor / plant engines with no silencer, the turbo tends to silence them.
The engine is a Cummins B series 210 HP.
Anyone heard one running like this?
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Please think also about other persons. The noice from boats without silencers are disturbing others, so from that point of view you should silence as much as possible.
 
piratos said:
Please think also about other persons. The noice from boats without silencers are disturbing others, so from that point of view you should silence as much as possible.
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Fair point, but I don't expect that you will hear it!!

I must admit I have the same opinion on light aircraft that fly over our house. I think that they must have no silencers as they can be heard for miles.
 
Most light aircraft don't!!

My Princess has nothing but 5" straight through pipes (TAMD 61A's) and I love the noise. Admittedly the exhausts are partially submerged so that probably helps.

The only issue is a resonant drone at about 1800 rpm, but I just don't drive in that region. The resonance is almost certainly unique to my installation though - length of pipes, deck resonance etc etc..

Latestarter will know :)
 
Barleycorn said:
Fair point, but I don't expect that you will hear it!!

I must admit I have the same opinion on light aircraft that fly over our house. I think that they must have no silencers as they can be heard for miles.
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Modern light aircraft are using silencers and have to comply with noise regulations.You will notice a considerable reduction in noise compared with old aircraft.
Many of the small planes flying around overhead are rather ancient perhaps well over 30/40 years old and were built in different era.Mere babes compared to the Moths and Stampes still wheezing around.
Noise control is a big concern for small airfield owners and pilots who ignore circuit noise rules do so at their peril. :)
Irate phone calls on Sunday mornings from " I know my rights" locals are relayed to errant pilots pronto
 
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Latestarter1 said:
The reason you get away with just 3.5 inch exhausts with that power output is simply because they have no mufflers
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Thanks Paul, I know I am living on the edge, one outstanding job is to put a port on the elbow and temp and pressure. The mitigation is that aside from the occasional squirt in calm water for maybe half a mile its never going full bore and is still a little under propped so never developing the full hp.
 
burgundyben said:
Thanks Paul, I know I am living on the edge, one outstanding job is to put a port on the elbow and temp and pressure. The mitigation is that aside from the occasional squirt in calm water for maybe half a mile its never going full bore and is still a little under propped so never developing the full hp.
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No Ben I am actually on your side, do not approve of arbitrary numbers, inexact science due do impact of water volume, it all works for you so life is good.

Sadly you can never safely extract 100% the ticket horsepower of a marine engine, only about 85% however as engine manufacturers sell engines by £ per hp seems a little unfair but that's life.

Seems like our friends from Europe appear intent on placing arbitrary ban Detroit strokers.
 
My Perkins exhaust runs straight out of the stern at the waterline, when underway it is submerged which acts as a silencer, it has no flap as the engine is way above the water line.
 
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