Mine is mounted center aft (I recall yours is on the side - port? ) and I haven't really noticed it. I'll pay more attention this summer - and I'll follow your solution...

 

I had the same issue. I replaced the entire rail assembly that included new engine mounts/dampers on my 7.6 and it made a big difference in eliminating mechanical noise/vibration to/thru the hull. I have purchased, but not added some air compressor pads. I think this would help. My biggest complain now is that the location is right below the engine compartment air inlets, and that is a big source of airborne noise. I keep contemplating adding a fabric noise shield, but measuring/installing is a major hassle.

 

I had the same issue. I replaced the entire rail assembly that included new engine mounts/dampers on my 7.6 and it made a big difference in eliminating mechanical noise/vibration to/thru the hull. I have purchased, but not added some air compressor pads. I think this would help. My biggest complain now is that the location is right below the engine compartment air inlets, and that is a big source of airborne noise. I keep contemplating adding a fabric noise shield, but measuring/installing is a major hassle.

View attachment 120384

Those look good but the leverage needed to get those installed would be a challenge in my boat. I never understood why they didn't bracket these generators into the stringers with a stainless frame and another set of engine mounts? I know it was all to do with BOM $$$

 

I purchased new mounts for my 7.6btd, the vibration throughout the boat when it's running is getting unbearable. I have yet to install them, I can't for the life of me figure out how to raise the generator up enough to get them changed out.

I also need to figure out a sound shield solution to knock down the engine noise. Last summer I added a dual lift muffler, as well as a second inline muffler. That really helped my external noise, but I need to figure out the internal noise now.

 

I purchased new mounts for my 7.6btd, the vibration throughout the boat when it's running is getting unbearable. I have yet to install them, I can't for the life of me figure out how to raise the generator up enough to get them changed out.

I also need to figure out a sound shield solution to knock down the engine noise. Last summer I added a dual lift muffler, as well as a second inline muffler. That really helped my external noise, but I need to figure out the internal noise now.

I replaced the entire rails. I used a couple 2x4's to wedge up under and as a lever to move the generator. Very doable.

http://clubsearay.com/index.php?threads/westerbeke-7-6-btd-vibration-noise-reduction.95727/

 

Following, our gen is not bad throughout the boat but laying in bed in the forward berth the sound seems concentrated. Not bad by any means but could be better. Seems biggest obstacle is lifting the gen to get more isolating material under the supports. Curious of the outcome.

 

Check these posts on the 360DA thread.
http://www.clubsearay.com/index.php?threads/calling-all-360-da-owners.26873/page-84#post-1287760
A little expensive but seemed like it could work to lift the generator enough to add new mounts.

 

I know vertical space is an issue, but, if you can get these in, they help a bunch, at least with hull-transferred noise. They're made with double-male, double-female, or male-female (easy, @Pirate Lady), depending on how best suits your installation. https://www.mcmaster.com/vibration-...ators/general-purpose-vibration-damping-sandwich-mounts-with-stud-and-insert-6/

 

I saw those; earlier today I contacted the Lord Corporation https://www.lord.com/products-and-solutions/vibration-and-motion-control/industrial/isolators and they started discussing natural frequency and harmonic frequency and static loads and dynamic loads. They pretty much sent me to the showers.... I have some homework to do....

 

Put it on the swim platform?

 

Or on the bow plywood...

 

I used 3/8” neoprene sheets when I replaced the mounts on mine. It made a difference for sure but then I did the sound shield and that’s the real improvement. It was a pain to measure and I went back and forth a few times. My major learning on the soft sound shield was it doesn’t need to be super tight. I was worried to make it fit perfect when another couple of inches around the gent wouldn’t have changed a thing.

while the neoprene did keep the unit somewhat decoupled from the plywood, I think proper engine mount isolators may have been better.

happy to discuss further is you want pictures or measurement but mine is a 10bdta

 

I used 3/8” neoprene sheets when I replaced the mounts on mine. It made a difference for sure but then I did the sound shield and that’s the real improvement. It was a pain to measure and I went back and forth a few times. My major learning on the soft sound shield was it doesn’t need to be super tight. I was worried to make it fit perfect when another couple of inches around the gent wouldn’t have changed a thing.

while the neoprene did keep the unit somewhat decoupled from the plywood, I think proper engine mount isolators may have been better.

happy to discuss further is you want pictures or measurement but mine is a 10bdta

Yes the entire issue is decoupling from the plywood. There is no exhaust noise other than splashing water and the sound shield does a great job. It is simply that harmonic and noise through the boat's structure.

 

These are the actual ones I purchased. Solid Rubber. If you give me a couple weeks, maybe I can get them installed and give you some real world feedback.

As you can see, I've had them a while, and with the new mounts, it hasn't been a huge priority, because I'm pretty happy what the new mounts have done to reduce mechanical noise/vibration to the hull.

There are other options that have neoprene or cork in them, and would likely be a little softer, or require a metal plate on top to prevent squashing them.

Like I said, this might be a trial and error type deal.

Dave

 

These are the actual ones I purchased. Solid Rubber. If you give me a couple weeks, maybe I can get them installed and give you some real world feedback.

As you can see, I've had them a while, and with the new mounts, it hasn't been a huge priority, because I'm pretty happy what the new mounts have done to reduce mechanical noise/vibration to the hull.

There are other options that have neoprene or cork in them, and would likely be a little softer, or require a metal plate on top to prevent squashing them.

Like I said, this might be a trial and error type deal.

Dave

View attachment 120412

Unless you use these pads on both sides of the plywood with a large bolt hole, you won't be isolating much at all. Like Tom said, the uncoupling is key. No direct metal to wood contact at all. My 21 KW Kohler has under water exhaust with venting through the port exhaust. From outside it sounds like a hair dryer on the lowest cool setting but when in the salon it is more than noticeable. This is going on the shorter list of updates for sure. In my case the frame on the genny is bolted directly to the hollow fiberglass stringers which I think amplifies the harmonics. I have about 10 inches of head room so installing isolators will be easier in my case. I think I will get some of the McMaster-Carr 1/2 inch bolt units. I had not ever considered looking there for isolators. This type would be ideal for further isolating the freshwater pump as well. Some dufus attempted to quiet mine down by screwing the pump to a stringer with a chunk of white Flexible PVC hose as a cushion.
Carpe Diem

 

True isolation is key. Here's one of may sources. https://www.gmtrubber.com/anti-vibration-mounts/

 

These might be something to look at. You would have to drill out a 3/4" hole in your pan, and likely add so shim material. Looks like these are a little less than 1.5" tall and have a load rating that would support the generator.

 

Also, those isolators I pointed to in an earlier post can be had in different durometers, allowing you to tailor the vibration frequency reaction. It's just trial and error, but, for their cost, it's worth it (to me) to experiment a bit to find what works best. I went through three sets on my Norton to get it right.

 

What generator and do you remember the part # or durometer?

 

In 2017 I replaced the old 2400 rpm NEXTGEN (had several issues) with a NORTHERN LIGHTS 1800 rpm generator.

The NL genset features factory mounts, internal to the case, however as an option, you can add 4 "biscuits" under the entire assembly. These are called ANTI VIBRATION MOUNTS.

(sorry I can't turn this photo)

Additionally, a flexible sound shield was added.

This design features a tubular aluminum frame with the soundshield basically wrapped in HD velcro to the frame, and to itself. Makes inspection and service a snap.

I had outfitted the previous genny with a GENSEP, separating the exhaust from the water output - another big noise changer.

Together, the end result is an amazingly quiet genset.

This is important to us as we run the genset nearly 100% of the time we're out on the boat for refegeration and A/C

Should the Kohler fail on the 450DA, I would go the same route. Northern Lights/biscuits/flexible sound blanket/gensep.

Hope my TROJAN experiences have some value here.

BEST !

RWS

 

View attachment 120477 In 2017 I replaced the old 2400 rpm NEXTGEN (had several issues) with a NORTHERN LIGHTS 1800 rpm generator.

The NL genset features factory mounts, internal to the case, however as an option, you can add 4 "biscuits" under the entire assembly. These are called ANTI VIBRATION MOUNTS.

View attachment 120475

(sorry I can't turn this photo)

View attachment 120476

Additionally, a flexible sound shield was added.

View attachment 120478

This design features a tubular aluminum frame with the soundshield basically wrapped in HD velcro to the frame, and to itself. Makes inspection and service a snap.

View attachment 120479

I had outfitted the previous genny with a GENSEP, separating the exhaust from the water output - another big noise changer.

Together, the end result is an amazingly quiet genset.

This is important to us as we run the genset nearly 100% of the time we're out on the boat for refegeration and A/C

Should the Kohler fail on the 450DA, I would go the same route. Northern Lights/biscuits/flexible sound blanket/gensep.

Hope my TROJAN experiences have some value here.

BEST !

RWS

I've had the soft sided sound sheild quoted, just hasn't made it to the top of the list just yet. It would be higher on my list, but getting it laid out and installed seems like a bigger project than I'm up for right now.

But this is a great discussion on how to quiet gennys down.

 

The good thing about generators is they run at a constant speed, so the decoupling frequency is not difficult.
That is 1800 RPM divided by 4 (four stroke engine) times 4 (4 cyclinders) = 1800 compression and firing pulses per minute. That is what we need to dampen. Then divide by 60 (Hertz is in cycles per second) = 30 hertz. Now if that 30hz is close to the natural frequency of the generator the amplitude to be damped can get large. But, let's assume that the engineering done on the generator has already taken that into consideration and not worry about it.
The existing isolators do a good job decoupling the generator machinery from the sound enclosure but there is still quite a bit of vibration on the sound enclosure and that is transmitting to the plywood deck and hull structure.
I think the issue is 30hz but less amplitude than actually on the engine due to the installed dampeners.
So, I'm down to some low profile conical dampeners that will support the generator's weight (695 pounds) and tuned to 30hz dampening in all axis.
It seems to me also that the plywood subfloor is a big part of the noise, a soundboard, and possibly should be changed to a more dense material or glued/bonded to the hull stringers.

 

I dusted off my old mechanisms book and ran through some calcs. If this is correct these need to be rather robust. One issue is can the pan/sound enclosure be carried on four points; I don't think so. Need to investigate further....

 

I dusted off my old mechanisms book and ran through some calcs. If this is correct these need to be rather robust. One issue is can the pan/sound enclosure be carried on four points; I don't think so. Need to investigate further....
View attachment 120547 View attachment 120548 View attachment 120549

30Hz would make sense, as the worst drone I notice with any engine configuration is right around 2000rpm which works out to be 33.3Hz. My wife agrees with that frequency being the most obnoxious (so it's not just me). A thought I had earlier was getting mounts with a low enough Durometer to isolate the vibrations, yet strong enough to handle the boat's movement as it's crashing through the breakers. When you question the enclosure being carried on four points, is this your concern also? Something like https://www.mcmaster.com/64885K33/ with a lower Durometer of 50A might decouple things nicely, yet still have enough strength to safely contain the genny's movement. With a diameter of 2" and OAL of 1-1/2", I'd think you could fit them underneath the genny. No matter the arrangement, a safety strap of sorts to contain excess movement in the event of a mount failure wouldn't be a bad idea.

 

Interesting Tom. I guess I don't notice it. The A/C we are sleeping on top of is much more noticeable.