Water/exhaust separator

[Osprey73]

Anyone having any experience from exhaust systems fitted with water separator? There was an article in PBO this spring claiming substantial noice reduction by removing the water sloshing from the exhaust outlet. Which sounds reasonable. Comments anyone?

 

[VMALLOWS]

I remember that article, but the system suggested seemed rather convoluted to me. Of course, boats with 'wet' exhausts will normally have a water 'trap'. However many (notably it seems Westerly's ..... I can always hear them coming) do not have any form of silencer after the 'trap'. In my experience a silencer just before the exhaust port along with a good 'swan-neck' formed in the rubber hose really reduces the noise.

 

[ean_p]

I think the way it works is.....water and gas are seperated and the water is ejected below the waterline and the gas goes out above the water line..the effect of the mixing of the water and gas at the manifold is that the water both cools the gas and the exhaust pipe and also silence the exhaust so that by the time the gas is ejected it is very quiet and as there is no 'splash 'of water then the whole is very quiet....

 

[ccscott49]

only seen them for generators, but I guess they could be fitted to small main engines. I just put a cowl pointing down over my genny exhaust, now the water hits that and runs down the side of the bootopping, so no splosh, splosh, cheaper aswell!

 

[dickh]

I think they were originally designed for generators, but no reason to suggest they could not be fitted for the main engine. The only reservation is that the water exits under the waterline, therefore is another potential hole if there are any problems. My boat has a water trap and a substantial swan neck, both in stainless steel, made I believe before they were generally available from people like Vetus. I get very little noise from the outlet and the splashing is not noticed above the general noise. The outlet is about 6" above the waterline.

dickh
I'd rather be sailing...

 

[Guest]

The water does not have to exit below the waterline. Provided there is adequate capacity in the system and or an adequately large vapour outlet the water can exit above waterline and will just be a steady, unpresurised flow.

 

[david_bagshaw]

Firstly, welcome to the forum.....

Have a haylard one fitted to an Onan 7.5 Kva generator, supplied as part of the installation kit.

The device is like an ordinary swans neck but larger with an additional connection to drain off the water, which is run off underneath the water line. which hast to be suprisingly large 1 1/4 in our case.
Effect as others have mentioned is to remove the splosh from the exhaust and cool it at the same time.


The reduction in Noise Is really dramatic … to the extent we have been in very quiet Harbours, and the harbour master has told us, “don’t start your generator here,” while standing next to the exhaust outlet, while the set was running at ¾ power.
it really is that quiet.

No I dont have any connection with either Hallyard or Onan , other than as a user.

Definitely a must have item

The only down side is it is not easily possible to check water flow rate from the sea water pump.


David
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[Luke]

I'd always been led to believe that the majority of the noise came from hull borne transmission through the propshaft and engine mounts and that, after noise insulation of the engine compartment, the biggest win was through a flexible drive coupling and softer engine mounts. Anyone have any experience to confirm/contradict?

 

[ean_p]

Yeah I have stood on the quay side of a local marina while they launched a 48 ft plus heavy traditional ketch...and when she moved away from the launch area the only way that i could tell her engine was running was by seeing the wisps of smoke from her exhaust.....it was that quiet....in terms of distance i was possibly 15/20 ft. No idea how it effects noise down below though as yes alot of this is vibration and machinary noise.....but i was left impressed thats for sure....

 

[david_bagshaw]

you are probably right but in generators, which are softly mounted any way, as there is no drive train, exhaust noise is more prevelent, plus gennys are used much more when the ship is in a quieter mode, so it is silence at any cost.

David
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