Lowering the Engine Noise Level

[jjmparsons]

Recently the wife and I took a trip with the family to Ono Island Al, and while there had the pleasure of riding on the home owners center console with a Yamaha outboard on it. I was blown away by how quiet the motor was. I honestly thought there was a smaller trolling motor that was powering the boat as we were slowly cruising along and was in utter shock to find out, no, thats the actual motor that running. Sadly, this has become a peeve of mine now as we take out the trusty jet boat and are cruising along at speeds where we cannot even hear the radio or have to throttle down just to have a conversation. The wife and I honestly spend the majority of the time with the boat off and just sitting on it as the flow of water takes us down the TN River so the noise is not a big deal at that time. @swatski I know I have seen a conversation between yourself and someone else in regards to using a garage door seal along the engine hatch lid but I cant seem to find it now. Has anyone else had any notable success in somewhat quelling the engine noise or at least bringing it down a notch or two?

 

[S1LV3R4D0]

Waiting for replies as i wanna deaden that sound too.

 

[jjmparsons]

Waiting for replies as i wanna deaden that sound too.

View attachment 103285

I recalled something about Duck Seal, searched and found where it mentions using some on the engine hatch but its not the original thread. There was quite a bit more indepth info on sound blankets etc if Im not mistaken.

https://jetboaters.net/threads/engine-compartment-seal-head-storage-upgrade.23539/

 

[S1LV3R4D0]

I see alot of sound deadening foam in those pics of his also. I went through his posts to see if he had one about that mod addition to no avail. Mine came stock with "some" but not like that looks.

 

[Speedling]

I installed the sound down kit from jet boat pilot and it did a lot. Still have leftover pieces and plan on doing the sides of the engine bay. It was a good bit louder because i had my soundproofing fall out. There are tons of install threads to search!

 

[Speedling]

The 82 db was at 8,000 rpm on a mr-1 doing about 35. Low profile windows as well

 

[Luc Lafreniere]

In case it interests you... I did soundproofing on my Scarab 165. PLENTY of info AND measured results can be found here: https://jetboaters.net/threads/scarab-165-mods.17479/page-2

Start at post #34 onwards. Actual results are at post 39.

In short, managed to reduce the decibel levels half 10db which is about equal to a HALVING of noise levels as perceived by the human ear. 3db is an actual drop of half the energy, but apparently you need about 10db so a person perceives it as half the noise. I can now listen to music and such while underway.

 

[swatski]

Recently the wife and I took a trip with the family to Ono Island Al, and while there had the pleasure of riding on the home owners center console with a Yamaha outboard on it. I was blown away by how quiet the motor was. I honestly thought there was a smaller trolling motor that was powering the boat as we were slowly cruising along and was in utter shock to find out, no, thats the actual motor that running. Sadly, this has become a peeve of mine now as we take out the trusty jet boat and are cruising along at speeds where we cannot even hear the radio or have to throttle down just to have a conversation. The wife and I honestly spend the majority of the time with the boat off and just sitting on it as the flow of water takes us down the TN River so the noise is not a big deal at that time. @swatski I know I have seen a conversation between yourself and someone else in regards to using a garage door seal along the engine hatch lid but I cant seem to find it now. Has anyone else had any notable success in somewhat quelling the engine noise or at least bringing it down a notch or two?

https://jetboaters.net/threads/another-soundproofing-thread-the-raamat-experience.11872/

 

[Speedling]

In case it interests you... I did soundproofing on my Scarab 165. PLENTY of info AND measured results can be found here: https://jetboaters.net/threads/scarab-165-mods.17479/page-2

Start at post #34 onwards. Actual results are at post 39.

In short, managed to reduce the decibel levels half 10db which is about equal to a HALVING of noise levels as perceived by the human ear. 3db is an actual drop of half the energy, but apparently you need about 10db so a person perceives it as half the noise. I can now listen to music and such while underway.

Love that man! I need heavier shocks as well now. Mine don't exactly do the job anymore with all the weight!

 

[S1LV3R4D0]

I ordered some of the duck garage seal to start. Shall see how well that does alone and go from there.

 

[swatski]

In case it interests you... I did soundproofing on my Scarab 165. PLENTY of info AND measured results can be found here: https://jetboaters.net/threads/scarab-165-mods.17479/page-2

Start at post #34 onwards. Actual results are at post 39.

In short, managed to reduce the decibel levels half 10db which is about equal to a HALVING of noise levels as perceived by the human ear. 3db is an actual drop of half the energy, but apparently you need about 10db so a person perceives it as half the noise. I can now listen to music and such while underway.

That’s great!
Along the same lines, I have about 25 cans of polyurethane foam injected inside various hull voids and more memory foam in large voids than a small mattress store, lol!

https://jetboaters.net/threads/filling-hull-voids-with-expanding-foam-good-idea-bad-idea.17966/#post-309944

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[Luc Lafreniere]

@swatski I think I over did it with 120lbs per spring though.... lol I think in my case, 100 MAYBE 110 would have been enough. Probably 100lbs. My hatch now pops open SUPER quick and needs a decent amount of pressure to close. I may buy weaker ones at a later date.

Suppose to have been @Speedling lol But @swatski yeah, I feel like doing that but can't bring myself to doing it. It would suck in the case of the 165 to run electrical or whatever in the future.

 

[dnicholas47]

https://jetboaters.net/threads/another-soundproofing-thread-the-raamat-experience.11872/

How did you put the rubber sealer around the hatch? Was it all in one piece, or did you cut into sections? I recieved mine last week, but just pulling it out of the box it seemed like it would be tough to keep it in one piece by yourself without it potentially getting glue places you didn't want it. (Admittedly I am not great with stuff like this, so if you have any egine hatch sealing for dummies advice I am all ears).

 

[S1LV3R4D0]

How did you put the rubber sealer around the hatch? Was it all in one piece, or did you cut into sections? I recieved mine last week, but just pulling it out of the box it seemed like it would be tough to keep it in one piece by yourself without it potentially getting glue places you didn't want it. (Admittedly I am not great with stuff like this, so if you have any egine hatch sealing for dummies advice I am all ears).

@swatski has a good little pic on which way to face it and where to put the glue here.

https://jetboaters.net/threads/another-soundproofing-thread-the-raamat-experience.11872/post-204592

 

[jjmparsons]

https://jetboaters.net/threads/another-soundproofing-thread-the-raamat-experience.11872/

YES!!!! This is the thread I had read through previously! Thanks!

 

[dnicholas47]

@swatski has a good little pic on which way to face it and where to put the glue here.

https://jetboaters.net/threads/another-soundproofing-thread-the-raamat-experience.11872/post-204592

I saved the picture. The stuff is kind of flimsy, and just trying to lay it out without any glue I couldn't figure out how to make it all the way around by yourself without any issues. I was hoping if there were any tricks or tips for dummies someone could share.

 

[Speedling]

I saved the picture. The stuff is kind of flimsy, and just trying to lay it out without any glue I couldn't figure out how to make it all the way around by yourself without any issues. I was hoping if there were any tricks or tips for dummies someone could share.

I had a similar seal and used brush on contact cement so i could stick a bit at a time. I cut into 3 pieces

 

[Gym]

Just to get back to @jjmparsons origional concern...The jets are noiser for a couple of reasons. First most of the horsepower, thusly its speed, is generated at the higher rpm range. Secondly inboards are enclosed within the boat so sound and vibration as not dissipated to the atmosphere like outboards. Last but not least you are comparing your twin engine jetboat to a single engine outboard. Yes a twin outboard would still be quieter than our twin inboard. You will have fewer headaches from noise with outboards but you will have more headaches with the initial increased cost and maintenance of the outboards. There is no perfect boat.

 

[Arcadyus]

The 82 db was at 8,000 rpm on a mr-1 doing about 35. Low profile windows as well

82db is when my shooting earmuffs start damping sound. My new pipes for my harley are only about 10db higher.

 

[tabbibus]

I saved the picture. The stuff is kind of flimsy, and just trying to lay it out without any glue I couldn't figure out how to make it all the way around by yourself without any issues. I was hoping if there were any tricks or tips for dummies someone could share.

That's the issue I'm having!