Cavitation, or is my boat just that loud?

[jamesk]

Out on the water yesterday, I stop the boat after running for 20 minutes.
My 72 year old mother (with poor hearing and needs to get hearing aids) says "oh good, quiet".
Then she tells me maybe we should wear ear plugs to protect our ears. ( wearing earplugs has already crossed my mind in the past).

I am already well aware of the noise and it's probably my biggest complaint with the boat.
I have already done a far amount of sound deadening mods and I also store lots of stuff like the covers in the storage compartments to help muffle the sound.

Boat is a 2017 sx210 with the newer tr-1 engines.

I know the prior owner sucked up atleast one tow rope.
Both engines seem to run well other than the noise.
Could the extra noise be from some type of cavitation issue?

If I am running a constant speed (20 mph for instance) the noise does seem to "peak" a little or slightly change volume level but overall it is fairly loud.

Maybe it is just loud but it has crossed my mind that maybe something else is going on?

Thanks! Jim

 

[jsg73]

What boats would you consider "quiet" at 20 mph?

 

[jamesk]

What boats would you consider "quiet" at 20 mph?

I have been on plenty of non jet boat (outboard and i/o) and they are no where close to this boat. 21 x like you have has different engines then what is on mine if I am not mistaken.

 

[OrangeTJ]

Of course, I have no idea what your boat sounds like BUT I will say that I felt the same way about our 2011 SX210. The boat was great overall but the level and nature of the noise it made at anything above no wake speed was frankly annoying. Couldn't really maintain a conversation without shouting. Our v drive inboard is much much quieter at all speeds and throttle settings. Maintaining a normal talking voice conversation at 20-25 mph is no problem at all. My sense is that with the jets, you have the combination of above-water exhaust, high rpm, and the noise of the jet drives themselves processing tons of water through the hull. Lots of great aspects of these boats, but in my own experience noise level isn't one of them.

 

[jsg73]

As others have said, a standard I/o is more like a Harley and a jet boat is more like a sport bike. I prefer to say the I/o is like a 4 stroke outboard and the jet is like a 2 stroke.
After comparing decibel readings between boats (it’s discussed somewhere on this forum), the sound levels were very similar at almost all speeds. However the jet does rev higher and is much more high pitched. I don’t see it any louder than my 150 horse 2 stroke at comparable rpm.

 

[Jim Davis]

How many hours on the boat? Bearings starting to wear maybe? You might try riding on someone else's Yamaha just to compare. Who know's you may have a problem starting to appear or it may just be normal.

 

[jamesk]

only 30 hours. Sounds like it just has a lot of "rumble" noise, not so much a "high pitched" tone.
Going to see if I can run it with the back deck open so I can see if some of the noise is comming from the water boxes.
There was a post about wrapping them in something like a yoga mat to help muffle the sound (my concern with that would be if there is too much heat around the water boxes...I don't know)
I was just trying to get an idea if "cavitation" could be a possible source of some of the noise..

 

[Jim Davis]

Gotcha Yeah I saw that about rapping the water boxes too but like you was worried about too much heat being trapped. I just don't know enough about it. Mine will cavitate during a turn sometimes but not straight ahead. Good luck and let us know what you find if anything.

 

[OrangeTJ]

Rumbling sound could be cavitation. Are you 100% certain that your clean out plugs are completely seated? The thing is, though, with cavitation you also experience performance loss. Does the boat pull hard and cleanly or does it feel a bit like it is "slipping" on acceleration?