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Old 04-16-2020, 04:56 PM   #1
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Anyone update old generator with new mounts and exhaust?

Hey guys. Boating in the south east with small kids means we literally run the generator when we leave the dock and donít shut it down until we get back to dock usually a few days later. When we anchor we are usually the only ones around so the noise of the generator isnít an issue, but I feel bad for the times there is someone else around.

The generator is an old 8kw Westerbeke with 5600 hours on her. I know thatís a lot but she really runs great. Itís noisy though. And thereís quite a bit of vibration. I own an old 5.9 Cummins in my truck and when I got it the motor mounts were shot. The vibration was unreal. New mounts fixed it and itís smooth as can be (for an old diesel).

The other thing is the exhaust. While the exhaust noise itself isnít bad, itís way louder than our mains, which are nearly silent. The water splashing is almost as bad as the exhaust noise itself.

A new generator is out if the question right now. But I figure mounts will be cheap and relatively easy. Not sure about the exhaust. Iíll save an underwater exhausts for the new generator.

So what have you guys done to lesson the vibration and noise?

Thanks
Steve
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Old 04-16-2020, 05:53 PM   #2
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Onan MDJE

I think the major source of noise from my generator comes from the intake. The exhaust is relatively quiet.
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Old 04-16-2020, 06:10 PM   #3
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You can get Centek Vernalift muffler and GenSep systems that help a whole lot. Intake sound suppressors are available too. 5600 hours on a genset is nothing as long as basic maintenance is adhered to.
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Old 04-16-2020, 07:42 PM   #4
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sound suppression on gensets

I just finished supressing some of the sound on my genset.

I have a Northern Lights 5kw with a sound enclosure in my lazertte.

I had structural vibration noise so what I did was I increased the size of the plywood generator shelf to 3/4" plywood and installed rubber sound mounts between the generator base (a 3/8" plywood board) and the newly installed 3/4" plywood shelf which is installed on a frame within the lazertte. The frame itself rests on 1" rubber belting, cut from a conveyor belt.

I found noticible sound relief.

The only thing left to do now is to install an exhaust/water seperator at the exhaust exit. I saw one video of a guy who put an extra exhaust inboard and inline of the exsisting whater muffler.

Question to Duvie. What do you mean by sound on the intake? Do you mean air through the filter or intake to the cylinders?
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Old 04-16-2020, 07:49 PM   #5
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Most bigger marine diesels have air silencers on the intake in place of a air filter. On the ocean you don't run into dust and an air filter can restrict the air flow too much.
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Old 04-16-2020, 07:50 PM   #6
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I would change out the mounts, Soundown sell some that are supposed to help with noise. Then I would increase the thickness of the deck where the genset is mounted and if you can get to the underside add a stiffener to the bottom, like a 2x4 glued and screwed to the underside of the mounting platform. Make the platform as solid as possible. Like was suggested above, it will help with the vibration and noise.
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Old 04-16-2020, 07:58 PM   #7
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You can make an intake silencer out of a rubber tube/hose attached to the intake. Route this hose to chamber hopefully cylindrical to reduce “oil canning”.

Re vibration mount generators to very substantial surfaces stiff enough and heavy enough that it won’t become a sounding board.
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Old 04-16-2020, 09:11 PM   #8
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Thanks for the advice! I had no idea that a sturdy base would have anything to do with it. Makes sense though. I was thinking about starting with ripping the old insulation out and replacing it with dynamat. I think a water separator will make a big difference. That’s down the road.

A 2nd in-line muffler would probably really help.

I’ll look into the induction noise also. It is pretty loud.

Thanks guys!
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Old 04-16-2020, 09:29 PM   #9
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Yes, a sturdy base will definitely help. I made one out of 2 layers of 3/4Ē plywood that I laminated together with epoxy and screws. Then I added a stiffener to the bottom. Whatever you do make sure it is solid.
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Old 04-16-2020, 10:41 PM   #10
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New mounts are a comparatively cheap and simple way to take out heaps of vibration from an older genset.

Hamish.
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Old 04-16-2020, 10:46 PM   #11
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I have a 3 year old 5.5 Westerbeke in an enclosure, on a platform 1 1/2" thick. The platform is mounted solidly on top of 2 stringers. The generator is directly below the salon. Very little vibration.

The exhaust consists of a Vetus Dual Stage Waterlock Muffler and a Centek GenSep water separater with the recommended hose loop. It is very quiet.

Other boaters think that an AC or frig is running instead of a generator. We can run it for hours without irritating anybody.

The GenSep is highly recommended.
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Old 04-17-2020, 05:36 AM   #12
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Some excellent advice above. From the bottom up:
A stiff structure to support the generator allows the isolation mounts to do a better job. The shelf itself and the supporting structure, sometimes braces and gussets depending on the installation.

What grahamdouglass described "installed rubber sound mounts between the generator base (a 3/8" plywood board) and the newly installed 3/4" plywood shelf" is called secondary isolation. This is not replacing existing mounts, but adding a second set between the frame of the generator and the shelf. This can often make a big difference. For a 500lb 8Kw unit these should not cost more than $50 each. Replacing the OEM mounts if over 10 years old is a good idea as well.

Enclosure insulation: Dynamat is a sheet metal damping product. Most small generators use 1" acoustic foam for insulation. A better upgrade than Dynamat would be 1" 1lb vinyl / foam insulation. The addition of the 1lb barrier increases the performance over the OEM acoustic foam. Make sure the air intake baffle on the enclosure is intact and lined w insulation.

A Centek Gen Sep in 2" from several sources is less than $300. You should only need a short piece of new hose to make the connection from your existing lift to the Gen Sep, and your existing to the hull run of hose should reach the Gen Sep. The hard part will be finding a way to discharge the water (1.5") below the waterline. Until your next haul out maybe you can find a thru hull to use, even an above the waterline thru hull which will still be quieter than the gas and water exiting together as they do now.

The air intake noise described above is particular to natural aspirated diesels, this is not a turbo diesel issue because the intake circuit is closed on a turbo diesel. An AirSep like Walker offers as well as others, work well to reduce this intake stroke noise which is low frequency and difficult to reduce once airborne. The hose technique Willy mentions makes the noise travel further and make several degrees of turns which reduces that noise.

$0.02
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Old 04-17-2020, 06:50 AM   #13
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Donaldson makes a nice air filter/silencer for things like skid-steers and small tractors with similar sized diesels. Does a good job of getting rid of intake noise, which on a 3 and 4cyl can be a lot of the noise. Can be mounted remotely and plumbed with tubing and hose sleeves.

Look also at your water lift muffler. Little ones don't do as good a job as bigger ones. If using a little one, see if you can fit in a bigger one. Wont help much with the splashing. but you are not at that point yet as you told.

If mounts are degraded, fresh rubber can really help too.
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Old 04-17-2020, 08:34 AM   #14
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All things have natural resonances including vibration isolators. Also isolators are designed for both vertical and horizontal loads. Lower frequencies generated with single cylinder engines usually present the greatest difficulty to isolate. I suggest that before you rush out and purchase new isolators that you get product specifications showing frequencies vs attenuation and loads, both vertical and horizontal from the isolator manufacturers and determine which can provide the best solution for you.

I am critical of isolators that allow height adjustments on a threaded shaft especially for horizontal forces. A better way to correct for height adjustments is to shim under the isolator.
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Old 04-17-2020, 02:50 PM   #15
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I have a 8.0 Westerbeke as well and HATE the noise.

I put a second, inline centek muffler onto it along with upsizing the centek lift muffler. It make a world of difference.
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Old 04-17-2020, 03:10 PM   #16
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The newer sound enclosure are well designed to contain noise. They muffle the noise with baffled apertures and tightly gasketed openings.

Sound enclosures are no longer a simple box around a generator. The new ones are engineered to isolate vibration and contain noise effectively.

Add effective water lift mufflers and Gen Seps and the generator will be really quiet. The biggest noise reduction is from the lack of exhaust water noise with the GenSep. The dual chamber Vetus water lift muffler also reduces the exhaust noise significantly without increasing back pressure.
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Old 04-18-2020, 06:17 AM   #17
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For max quiet a more complex system is required.

The unit is mounted on a frame with soft mounts , then the frame itself is mounted on soft mounts .

Works both for an engine and the noisemaker , but the hookups must be very compliant to handle the motion, and not pass on sound.

Usually too much expense except for Gov .
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Old 04-20-2020, 11:08 AM   #18
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Thanks guys. I think my plan of attack is going to be to take care of the vibration first since that’s the biggest problem and the cheapest and easiest. So how are you guys lifting the genset high enough to redo the shelf?
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Old 04-20-2020, 11:16 AM   #19
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A wet muffler and sound shied sounds like good advice. I have an Onan 8K in my cockpit. My A/C makes more noise than the genny.
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Old 04-20-2020, 12:10 PM   #20
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Quote:
Originally Posted by Steve91T View Post
Thanks guys. I think my plan of attack is going to be to take care of the vibration first since thatís the biggest problem and the cheapest and easiest. So how are you guys lifting the genset high enough to redo the shelf?
With an electric winch hung from a 4" X 4" straddling two sawhorses.
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