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Old 05-11-2018, 09:09 AM   #1
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Onan sound insulation?

Anyone replaced the sound-deadening insulation on their Onan generator?

I've got an 13.5kW Onan MDKAZ diesel generator on board and the survey pointed out the insulation inside the housing is failing. I'd like to avoid the dust/chunks becoming any sort of ingestion/filter issue.

I came across a parts diagram

Seeing as how it's a lot of pieces and some pretty tight quarters I'm thinking that sticking with the factory pre-cut sections would be the least hassle. No doubt not the least expensive though.

Anyone recommend a reasonable source for the insulation pieces? Is there a kit for these as a set? Or am I just ordering them by their individual part numbers?
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Old 05-11-2018, 10:09 AM   #2
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I think you will have a hard time trying to find OEM foam. There are a lot of sound proofing products out there that you can R & R.....
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Old 05-11-2018, 10:24 AM   #3
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I think you will have a hard time trying to find OEM foam. There are a lot of sound proofing products out there that you can R & R.....
Possibly true, but I'd like to rule out OEM first. Or get a clear indicator of just how wretchedly expensive OEM would be compared to adapting something else.

I've installed various kinds of insulation in other situations and would prefer to avoid the considerable added time of templating/cutting/trimming if possible.
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Old 05-11-2018, 10:26 AM   #4
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You could try Jamestown Distributors since they carry soundown material.
https://www.jamestowndistributors.co...RoCHxsQAvD_BwE

So does Amazon.com as well...
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Old 05-11-2018, 12:28 PM   #5
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A friend used these guys for a similar project. Turned out great. Worth giving them a call. Our Products | Great Southern Insulation
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Old 05-11-2018, 12:41 PM   #6
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A friend used these guys for a similar project. Turned out great. Worth giving them a call. Our Products | Great Southern Insulation
It appears they also market a sound-deadening cover. That might be an interesting avenue to consider as well. I'll contact them, thanks for the link.
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Old 05-11-2018, 04:07 PM   #7
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Had the exact same issue with our Onan, the disentegrating foam started going everywhere, and could not find or purchase the OEM foam at any price (at least here in Australia).

Ended up having to buy an alternate product, roughly cut it to size and glue it to the inside of the sound shield.

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Old 05-12-2018, 05:29 AM   #8
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You will not find an aftermarket pre cut kit for this, doesn't exist. Any Onan Dealer can order it for you if its still available.

In the aftermarket as a sheet product the replacement foam insulation is available with peel and stick adhesive if you look for it, makes the installation much easier and helps get the insulation under the "lip" found an the back of many hard panels. The job isn't bad at all, the panels come out, and the hard part is cleaning off the old insulation.

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Old 05-12-2018, 07:24 AM   #9
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I have 2 generators, the smaller is a Onan 14 kw. I wanted to make one as quiet as possible. I replaced the existing sound proofing with newer material, but the biggest noise change was putting 2" foam under the enclosure so the vibration and noise isn't transferred to the hull structure.
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Old 05-12-2018, 01:31 PM   #10
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What you did is called secondary or double isolation, very common on larger yachts, actually more effective on smaller boats and a big improvement in reducing noise levels.
It is best done with isolators and not foam, almost every marine genset is set up for where the mounting holes are to carry the weight of the genset as the manufacturer assumes secondary isolation. The 4 hard points are typically spaced equally from the C/G so the 4 mounts are equally loaded.
The weight needs to be considered for selection, something similar to the unit below will only require 1.5" or less

Changes the vibration from "I can feel the generator running" to "I think I can feel the generator running."



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but the biggest noise change was putting 2" foam under the enclosure so the vibration and noise isn't transferred to the hull structure.
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Old 05-12-2018, 05:26 PM   #11
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Quote:
Originally Posted by Lepke View Post
I have 2 generators, the smaller is a Onan 14 kw. I wanted to make one as quiet as possible. I replaced the existing sound proofing with newer material, but the biggest noise change was putting 2" foam under the enclosure so the vibration and noise isn't transferred to the hull structure.
Which, I take it, took some re-plumbing of various hoses and such?

I get your point, it's the same sort of thing for home theater setups. The key being de-coupling the thing making the rattling from adjacent surfaces that would transfer it. Better to have the vibrations dampened by the foam rather than directly passed along to the hard points used for mounting. For theaters there's none of the weight involved though, just clips, adhesives, layers of drywall and the like. But mostly the purpose is the same.

I'll pull off some of the panels to get a better look at what I'm dealing with. If I have a chance to improve the situation with different, more modern materials it may well be worth the added labor to trim them to fit.
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Old 05-12-2018, 06:06 PM   #12
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Most of the wiring, plumbing and exhaust hooked into a marine generator are pretty forgiving of inch or 2 of vertical rise. Foam is not preferred for several reasons. It doesn't provide "positive capture" unless you use extra long bolts to secure it which short circuit the isolation. It's also difficult to calculate how much foam is just right for the deflection you want. A mechanical isolator does all those things very well, it's what they are designed to do.

As for "more modern materials," anything beyond a vinyl/foam insulation with a 1lb barrier is wasted. The "baseline" for airborne noise from a generator will be from the combustion air inlet, and anything that performs better than a vinyl/foam insulation with a 1lb barrier is just additional weight and expense that bring nothing to more performance.




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Which, I take it, took some re-plumbing of various hoses and such?

If I have a chance to improve the situation with different, more modern materials it may well be worth the added labor to trim them to fit.
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Old 05-12-2018, 06:06 PM   #13
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The generator floats on the foam. Brackets with rubber keep the generator from moving in heavy rolls. Connections are flexible so the plumbing, etc., doesn't pick up the vibration.

Where I got the foam idea - I was using a vacuum pump for some fiberglass work. About a 1hp motor/pump (with rubber feet) and it was noisy. It was driving everybody to distraction. One of the guys grabbed a 2" piece of foam, put it under the pump and it was at least 50% quieter. Since then, I've been using foam along with other materials for sound quieting.
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Old 05-12-2018, 07:26 PM   #14
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The worst part of replacing the sound insulation has to be removing the panels to r & r the insulating material. The actual replacement would be easy. I still remember having to remove panels to get at a dropped coolant cap(normally accessed via a small hatch in the saloon deck).
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Old 05-13-2018, 07:48 AM   #15
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Heh, good advice on the dropped cap. I've had my share of work added to a task because of nonsense like that!
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