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Discussion Starter · #1 ·
My boat has sound insulation (1 inch foam sheeting with foil facing) on the bulkheads immediately surrounding the engine (Yanmar 2QM15). Not sure if it's original or PO installed, but I suspect the latter.

But the boat really doesn't have a true "engine room", so the bulkheads where the insulation is installed aren't continuous, which means that the engine is not encapsulated by insulation, and to my layman's way of thinking the sound can travel pretty much anywhere. For example, there is only a thin, uninsulated panel between the engine and quarter berth.

I removed some of the insulation to fix some wiring, and doing so made a big improvement in engine access clearances, so I'm thinking about removing it all.

Any reason I shouldn't do this, other than causing (possible) noise level increases?
 

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That insulation also prevents some heat loss... in summer a good thing, maybe in off season not such a big deal.

Here's a trick we've used to quiet things down that works REALLY well, and is easily removeable when engine access is required. If you can find/get one, drape a dentist's 'Xray apron' directly over the engine. Be careful to ensure that the air snorkel isn't blocked (one of the armholes works well) and avoid any bare hot exhaust piping - and, of course, any moving belts etc. It's quite amazing how much noise that cuts out right at the source. And no, it does not affect engine temperature!
 

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Discussion Starter · #3 ·
I never would have thought of that. I have a few dentist friends, so I'll see if I can get my hands on one. Thanks for the tip!
 

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Tartan 37
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Proper engine alignment can reduce a lot of sounds as well. The Sundown insulation is what I installed and it made a significant difference, especially heat.
 

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Good sound insulation does not have to be continuous to make a difference, but it is best if it is. Often just small patches on any flat panel, especially metal or fiberglass can be quite effective as it stops the panel from vibrating. Automotive car stereo stuff can be helpful. But I doubt a foam with one layer of foil does much more than keep heat in. (Keeps engine at operating temperature, and keeps it out of the cabin) The best foam for noise will have a sandwich of lead or other heavy foil in between two layers of foam. It will be quite a bit heavier than one would think by looking at it. I believe that is the foam that Shawn is referring to.
 

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I used sound down paint and also the 1'x1'x1" tiles from Sailor Solutions .. Haven't heard my engine run yet as it's not been started but it looks like a good job at least haha! Also, check out dynomat, you can get it in larger pieces on Amazon. Has sticky backing. It's only an 1/8" thick or so. Better than nothing and the metal film may cut on some heat too.

First picture is after I painted the 5 coats of the sound paint, and the second is after I took the old stuff down and then after I put the tiles over the sound paint.
 

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I had not yet finished all the final taping and also put a panel of the Sundown on the top, or under the cockpit floor. Beta told me NOT to enclose to engine in so it can "breath".
 

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so I'm thinking about removing it all.

Any reason I shouldn't do this, other than causing (possible) noise level increases?
My boat has a bit of quite crappy foam as sound proofing. In the aft cabin the back end of the engine bay is removable and theres a 1 cm gap so plenty of noise gets out.

But heres the thing, I have slept in that cabin at sea numerous times with the engine going. It just seems to blink off when I nod off! Weird.

So a noisy engine right next to someones head may appear to be a real pain, but its a constant noise and one soon gets used to it :)
 

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I had not yet finished all the final taping and also put a panel of the Sundown on the top, or under the cockpit floor. Beta told me NOT to enclose to engine in so it can "breath".
I just realized the belt is on the wrong wide of the cooling hose. Thats just dumb.....

"1st mate" Captain, the belt just broke, and we are taking 15' breakers on the beam.
"captain" Quick, disassemble the cooling system and change it.

As opposed to: belts broke, ok, loosen the alternator, put a new one on.

BTW I think beta is assuming the engine is being installed in a modern cookie cutter boat. Enclose it, a 3" hole is all it needs to breathe.

I love beta/kubota engines, but this was a poorly thought out design.
 
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