water lift muffler

[bostonhatteras]

Hello everyone
Does anyone have recommendations for a genset water lift muffler? There are quite a few brands marketed and I would imagine some are better than others. I assume that everything now is either in fiberglass or plastic. If you have experience with comparative noise levels, available drain plug, thinness or thickness-aka durability especially on the hose connections, I would very much like to know. The generator is the infamous but good running quicksilver 8.0D (diesel). The current muffler is a stainless steel version made by a now defunct company that was located in west newton ma. The name was Allcraft. Ive included a couple pics of it. The selection of muffler, once made, will be proverbially set in stone because it will be incorporated into a new shelf system and literally set into a recess in the shelf so different sizes will not easily be accommodated after the fact. Inlet and outlet are for 2'' hose. Thanks for the valuable insights, as usual.

 

[jim rosenthal]

I'd look for a Centek or a Vernalift. Probably in the Defender catalog. They are fiberglass, I believe.

 

[bostonhatteras]

Thanks I could pick any number of available designs. Id like to know which are the quietest and perhaps offer the drain plug. No one seems to advertise number of decibels they reduce the exhaust note by. I understand that the fiberglass tubes for hose connections can be a weak spot, crushing from over-torque of clamps and the tubes also coming adrift from the body of the muffler when hoses offer a long lever arm against it. Stainless steel didn't have any of those problems, just corrosion!

 

[SeaEric]

The outside noise is mostly created by the water gushing out with the exhaust gasses. Add a gen-sep to the water lift muffler if you truly want quiet. http://www.centekindustries.com/gas_water_separator.html

 

[bostonhatteras]

Ive listened to other generators and the noise is more than water gushing. clearly some waterlock/waterlift mufflers do better than others. I know that the water interacting with the exhaust gases does a considerable part of the quieting. The balance of noise has to be removed via the design of the muffler. im not so much concerned with splashing water.

 

[GJH]

Thanks I could pick any number of available designs. Id like to know which are the quietest and perhaps offer the drain plug. No one seems to advertise number of decibels they reduce the exhaust note by. I understand that the fiberglass tubes for hose connections can be a weak spot, crushing from over-torque of clamps and the tubes also coming adrift from the body of the muffler when hoses offer a long lever arm against it. Stainless steel didn't have any of those problems, just corrosion!

Read through the Centek site. They have a graph that shows typical attenuation. They are helpful on the phone too; I considered adding a Gen Sep to my boat but never got around to it. Most of the noise in our case was from the water, and after months on moorings and various anchorages, never got complaints so never bothered. No question the water splash is the biggest noise. They can also advise you on your tube crush paranoia.

http://www.centekindustries.com/choosemuffler.html

 

[fissioneng]

My OEM Centek Vernalift works great on my MDKD 8 kw. You have to get pretty close to the boat to even hear the water gushing. My AC pump discharge actually makes more noise.

I don't know about a drain plug since I never drain it.

Now if I can just quiet the darn thing down on the INSIDE I'd be happy.

 

[bostonhatteras]

Read through the Centek site. They have a graph that shows typical attenuation. They are helpful on the phone too; I considered adding a Gen Sep to my boat but never got around to it. Most of the noise in our case was from the water, and after months on moorings and various anchorages, never got complaints so never bothered. No question the water splash is the biggest noise. They can also advise you on your tube crush paranoia.

http://www.centekindustries.com/choosemuffler.html

Getting back to the point, if water splashing is YOUR biggest noise then perhaps you have a muffler that is designed well. Do you know what you have? I did look at the chart of sound attenuation and without comparisons to other brands of mufflers on the same engines in the same installation is about as good as saying 'ours are best'! Science is not made by one graph! No one has mentioned Vetus but I'm leaning toward their two chamber design 'NLP'. They make a vast number of muffler designs and give a reasonable explanation of why they choose the particular design as well as cross section drawings. The cross section drawing allow you to see the exhaust travel/interaction with water thoughout the process. Every Vetus muffler has a drain plug they are also plastic. Centek makes a lot of oem mufflers particularly for searay. The searay gas boats I know sound terrible. Centek also don't show cross section of the muffler. But they do have a graph. Lol. Btw the solution to tube crush is 'available' S.S.sleeve inserts. The sleeves kind of remind me of the fortress anchor mud palms that at first weren't there, then shipped free to anyone that wanted then and now are on every anchor sold.

 

[saltshaker]

I'm not 100% certain but I believe I have Centek Vernalift mufflers on my generators. I know I had one on my last boat and the boar prior to that. The generator on my last boat was so quiet I often thought it may have stalled out. You can't hear it from the bridge and the only noise is the water discharge. Also very quiet in the boat. I will note that this was a '99 Onan 12.5 with a soundshield. ER was also soundproofed with all new Soundown when I re-powered in '02, but it was also quiet before then. Mine did have a drain plug as do the ones on my current boat. The generators on this boat aren't as quiet but still pretty good. Very little sound outside the boat other than some minimal motor noise if you are near the ER vents. My generator exhaust dumps into the engine exhaust tubes so there is almost no exhaust or water discharge noise unless you get close to the discharge. I've changed the hoses on the last two boats and will be changing them this winter on this boat. Never had an issue with the tube crushing. Maybe that's more of an issue on the smaller units? I'll let you know how I make out when I do them and will check the brand next time I'm down there.

 

[jim rosenthal]

I have a Northern Lights genset and I bought the NL recommended waterlift muffler- which was made by Centek. It works fine. It does splash, though. That's function of the fact that the outlet is quite a ways above the waterline. Hatteras put it there and I wasn't bright enough to move it when I had the chance, so it's still there.

The best installation for low noise I have seen (without using a GenSep, and they do work very well) is one in which the water exhaust from the genset is run out aft through one of the drive engine exhaust tubes. (some Vikings I have seen have a separate small tube glassed into the inside of the main exhaust tube, for the genset exhaust water, also) That seems to work very well also.

 

[saltshaker]

The best installation for low noise I have seen (without using a GenSep, and they do work very well) is one in which the water exhaust from the genset is run out aft through one of the drive engine exhaust tubes. (some Vikings I have seen have a separate small tube glassed into the inside of the main exhaust tube, for the genset exhaust water, also) That seems to work very well also.

Mine have a separate exhaust pipe that is glassed into the top of the engine exhaust outlets. Works great and no additional holes in the hull. The exhaust system on my boat is pretty highly engineered. I have side exhaust, underwater exhaust and water bypass relief. The bypass valves open if exhaust pressure increases at all.

 

[GJH]

Getting back to the point, if water splashing is YOUR biggest noise then perhaps you have a muffler that is designed well. Do you know what you have? I did look at the chart of sound attenuation and without comparisons to other brands of mufflers on the same engines in the same installation is about as good as saying 'ours are best'! Science is not made by one graph! No one has mentioned Vetus but I'm leaning toward their two chamber design 'NLP'. They make a vast number of muffler designs and give a reasonable explanation of why they choose the particular design as well as cross section drawings. The cross section drawing allow you to see the exhaust travel/interaction with water thoughout the process. Every Vetus muffler has a drain plug they are also plastic. Centek makes a lot of oem mufflers particularly for searay. The searay gas boats I know sound terrible. Centek also don't show cross section of the muffler. But they do have a graph. Lol. Btw the solution to tube crush is 'available' S.S.sleeve inserts. The sleeves kind of remind me of the fortress anchor mud palms that at first weren't there, then shipped free to anyone that wanted then and now are on every anchor sold.

No need to be a d**k about it. You complained about not having any attenuation info and I gave you a link to one manufacturer who provides it. So now you are whining I didn't provide a few others to compare? Your welcome! Oh BTW, Centek has crush sleeves in their accessory section, they don't make them for the smaller units, you could ask them why. I am very familiar with these as noted in an older post of mine, having bought two ten inchers early last year from Hatteras for my main exhaust. Vetus makes nice stuff in general, and their US distributor, Florida Bow Thruster, is a pleasure to do business with.

My muffler is a Vernalift, but it does have a nice piece of Vetus exhaust hose attached to it and the 20kw Onan!

On those motoryachts where the generator is not in the ER, and well forward of it in a separate room, running the exhaust out the back sport-fish style isn't practical. I'd be careful about using a common exhaust tube for both genset and engine, all I can recall seeing is seprate tubes molded in as Jack notes.

 

[jim rosenthal]

George, I have seen retrofits wherein the generator set exhaust water flow was diverted into the aft exhaust tube at some point. It is extremely quiet, but I don't know that it is a good idea, as you pointed out. A better solution is what Jack describes on his boat, similar to what you saw and what I saw on the Viking convertible a few years back- a separate tube glassed into the top of the main exhaust tube, with a sidearm to connect it located near the origin of the smaller tube. The only thing you might have to allow for is that the length of the smaller tube might increase resistance to flow a little, but it couldn't be a huge amount.

I am not aware of any comparative data on generator noise reduction systems for exhaust water. Obviously every manufacturer will claim that theirs reduces the noise of exhaust water to the point where it is unnoticeable. Some will actually DO this and some will be, as they say, gilding the lily. The only way I can think of to figure this out is either to ask motoryacht builders if they compared the different systems, and see if they are willing to share their data, or call them and ask what they use (hoping they compared different systems and didn't just elect to use the cheapest one) or go look at a whole lot of boats and see/hear their gensets run. For my own boat, it is small enough and the generator is centrally located enough that the noise is more from the set itself, not from the exhaust water, so a GenSep wouldn't make a lot of difference if any. What mine needs is a sound enclosure, or hush hood- but none will fit and I have lost interest in trying to build one myself, I have too many other projects right now. Maybe later on. In a 36C Series I, there is nowhere to locate this generator set which will allow a factory hush hood to be used. Unless it went out under the after deck, which would mean taking the bait well out. And that's not happening.