Exhaust – muffler, silencer, water traps etc?

[carrswood]

Hi guys
I’m soon to be replacing my boats engine.
I’m slightly confused what exhaust setup to install. I see Vetus offer mufflers, silencers, traps etc etc

As a minimum what should I be fitting?
I’d put a silencer in to if it helped the noise levels.

 

[vyv_cox]

Hi guys
I’m soon to be replacing my boats engine.
I’m slightly confused what exhaust setup to install. I see Vetus offer mufflers, silencers, traps etc etc

As a minimum what should I be fitting?
I’d put a silencer in to if it helped the noise levels.

Is muffler American for silencer?

My Yanmar 27 and Bukh 20 before it had the same arrangement. Exhaust gases plus coolant pass downwards from the engine into the trap. From here they pass along the shaft tunnel into the lazarette, upwards to form a loop, then down to the skin fitting via a vertical silencer. The trap is firmly fixed to the tunnel floor but the silencer is mostly supported by the exhaust hose plus a couple of short lengths of line tied to convenient points. It's been like this since Sadler built it, so must be good enough. Very quiet installation.

 

[carrswood]

thanks for that - did you use VETUS products
I see some people reccomend a siphon with breather on the water inlet pipe - is that necessary too?

 

[vyv_cox]

thanks for that - did you use VETUS products
I see some people reccomend a siphon with breather on the water inlet pipe - is that necessary too?

Yes, my trap and silencer are both from Vetus.

Depends on the height of the engine relative to water level. If there is any risk that water could flood the engine then a loop to above maximum possible water level and siphon break are normally fitted.

 

[VicS]

The water trap (aka waterlock) is the minimum that should be fitted. It should be sufficiently large to collect and contain all the water that is left in the exhaust system when the engine is shut down.

A swan neck before the outlet in the transom is the next most vital thing as it will prevent water entering the exhaust system via the outlet.

A muffler is only required if additional silencing is required. The rubber hose on it's own is a pretty good silencer if there's a decent length!

The syphon break, usually in the connection from engine outlet to exhaust injection point, it a separate issue and it is recommended if the injection point is less than 15cm above the waterline. It should be positioned 40cm above the water line. (absolutely vital of course if the injection point is close to or below the waterline)

The Vetus on line catalogue is a good source of info.

 

[snowleopard]

As a minimum what should I be fitting?
I’d put a silencer in to if it helped the noise levels.

The minimum is a water lock. The ideal situation as recommended by Vetus is a waterlock followed by a muffler and finally a gooseneck to prevent water being pushed back up the exhaust and filling it with the risk of flooding the engine.

 

[Deleted member 36384]

On my own boat I only have an exhaust hose. It comes off the engine and drops down to the hull, then bends up to coach roof, where it goes into an up side down U bend. This first part of hose run has heat resistant insulation wrapped round it. the exhaust continues down again from the other side of U bend and turns under a locker before being attached to the skin fitting. So only a water trap for me.

To be honest its not that quite an installation. Rather than fit a silencer I am considering using more insulation to deaden the sound from the exhaust pipe.

If your engine is out paint the bilge area around the engine with sound absorbing paint. I think International or Blakes make it. It makes quite a difference.

 

[Leo2]

Vetus products are very good. If you want to save some money though, have a look here. http://www.boatpartsandspares.co.uk/vetus-84-c.asp They stock shop soiled and used (good condition) Vetus Waterlocks, Goosenecks, Mufflers, ect.

 

[snowleopard]

...It comes off the engine and drops down to the hull, then bends up to coach roof, where it goes into an up side down U bend....

That is pretty vital. The exhaust must lead downwards to the skin fitting so that any waves hitting the exit while the engine is stopped can't run back into the lowest part of the exhaust and fill it.

The Vetus gooseneck provides that height but also has a large diameter so that it can accept a lot of incoming water without overflowing back up the exhaust.

The waterlock provides a place for a large volume of water to drain into when the engine is stopped. Sources of the water are what's left in the pipe when you switch off, water pushed through during cranking if the engine doesn't fire right away (a lot with fresh-water cooled engines) and anything getting in from tha far end. A plain pipe will work but you'd need to be very careful not to keep cranking if the engine doesn't start easily.

 

[Tranona]

No, that is correct. See pp 168/9 of the Vetus catalogue www.vetus.com

 

[eastlaked]

Water Trap Connections

Slight thread drift.

Pat Manleys "Diesels Afloat" (Page 78 and page 111) shows the water trap with the engine side connection pipe going down to near the bottom of the water trap and the "Transom" side connecting just at the top.

To me this seems wrong. If the engine sucks back it will suck up water. When it runs normally its just going to fill up the entire water lock.

To me it makes sense if its reversed, ie transom side of the trap has a pipe to the bottom of the trap. Then the engine running pushes gas/water into the trap and the water at the bottom is blown up the pipe to the transom outlet. If the engine sucks then water won't get sucked up as the engine side pipe is short and out of the water sitting in the trap.

Are the diagrams in the book wrong, or is it my understanding???

 

[reeac]

Is muffler American for silencer?

My Yanmar 27 and Bukh 20 before it had the same arrangement. Exhaust gases plus coolant pass downwards from the engine into the trap. From here they pass along the shaft tunnel into the lazarette, upwards to form a loop, then down to the skin fitting via a vertical silencer. The trap is firmly fixed to the tunnel floor but the silencer is mostly supported by the exhaust hose plus a couple of short lengths of line tied to convenient points. It's been like this since Sadler built it, so must be good enough. Very quiet installation.

In answer to your first question - yes, in the automobile world "muffler" is American for "silencer".

 

[philip_stevens]

Slight thread drift.

Pat Manleys "Diesels Afloat" (Page 78 and page 111) shows the water trap with the engine side connection pipe going down to near the bottom of the water trap and the "Transom" side connecting just at the top.

To me this seems wrong. If the engine sucks back it will suck up water. When it runs normally its just going to fill up the entire water lock.

To me it makes sense if its reversed, ie transom side of the trap has a pipe to the bottom of the trap. Then the engine running pushes gas/water into the trap and the water at the bottom is blown up the pipe to the transom outlet. If the engine sucks then water won't get sucked up as the engine side pipe is short and out of the water sitting in the trap.

Are the diagrams in the book wrong, or is it my understanding???

If you are referring to the barrel shaped water trap, he is correct. I have one on my boat, and the engine exhaust is on the low side, and the outlet to the transom is on the high side.

Vetus - Page 168 shows the orientation

It might look wrong, but he is correct.

 

[snowleopard]

Is muffler American for silencer?

My Yanmar 27 and Bukh 20 before it had the same arrangement. Exhaust gases plus coolant pass downwards from the engine into the trap. From here they pass along the shaft tunnel into the lazarette, upwards to form a loop, then down to the skin fitting via a vertical silencer.

It's likely the vertical silencer is just a gooseneck- a box to hold any water being forced up the exhaust - certainly if it's made by Vetus that's what it is.

The Vetus 'muffler' is a flat plastic box with ribs in top and bottom that effectively forces gases and water through a series of baffles.

Here are the bits:

Muffler

Gooseneck

Combined waterlock & silencer

The above are links to eBay so won't be there very long.

Standard waterlock

 

[vyv_cox]

As I said, mine has a silencer (= muffler) vertically from the top of the hose loop down to the skin fitting. Definitely not a gooseneck. No idea whether this is the textbook installation but as far as I know it is how Sadler built it in 1984, it works well and is quiet.