Sound dampening SEM

[Wisefam22]

Found this product and wonder if anyone has seen/used before.

https://www.semproducts.com/product/dual-mixtm-sound-seal-sprayable-coating#product-details

It's a sound dampening epoxy mixture. Wonder how it would work, imagine we would need to use a ton of it. Was thinking about around engine hatch, fuel tank lid ect.

 

[jvegas]

following

 

[Jgorm]

I'm not sure any mass dampening is going to do much of anything on top of fiberglass.

 

[BlkGS]

Looks like a rubberized undercoating to me.

There used to be some liquid sound deadened that you painted on. I tried them on an old car of mine, and while it did work decent at stiffening the panel, it was MESSY. It was also smurf blue and if you got it anywhere you weren't intending, it was obvious and made a mess.

I think a product like that would work pretty well in this application. The fiberglass panels seem to reverberate with the frequency of the engines, bringing their resonant frequency down would quiet the boat down a good bit in theory.

 

[swatski]

The fiberglass panels seem to reverberate with the frequency of the engines, bringing their resonant frequency down would quiet the boat down a good bit in theory.

This is correct. Unfortunately MLV type soundproofing does not seem to work well on fiberglass (or even FRP like Yamaha new hulls). (just what @Jgorm said!)
It must be the ratios of fiberglass (mass) vs the sheath metal in cars? IDK.
But having invested time/labor/$$$ in some 200lbs of DYnamat Extreme in my old (2012) SX190, I would not recommend going that route. It helps but the effects are marginal compared to price and effort, a MUCH more efficient way is to fill the voids. For example, polyurethane foam works great, even scraps of closed cell foam or old ballast bags filled with air - stuffed up the gunnels - work much much better.

The easiest and best/least expensive/least labor intense sound proofing mod, which should be done as number one no doubt - is the engine hatch seal!

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