These jet boats are not going to be as quiet as an outboard, that’s just the way it is.
From my experimentation with different impellers, I can tell you that the skat trak impellers cut the perceived noise by half, sadly ended up having to use the Solas at least for the foreseeable future. I was using a db meter app on my phone to confirm this.. 3 DB is a perceived doubling or halving of a give noise level, the skat traks were 3 DB’s lower in noise than either the Solas or OEM impellers.
Also, my take is that a lot of the noise I get on my boat is wind noise. Is there engine noise? Yes of course, but the wind noise is what you have to raise your voice over.
When I did some long runs last summer at Lake Powell ( 1.5-2 hours) I used the original EAR foam ear plugs, they are super cheap, and easy to use and keep handy, they cut the noise by 29 DB’s. They are easy for me to use as I have been using them for most of my life, if it wasn’t for work then when I’m riding my dirt bike. To me, the benefits of the jet drive and the Yamaha boat design far out weigh the increase in noise over an outboard / I/O drive boat.
Here is boat tests data on the 255 FSH Sport E, best cruise speed at 27 mph=89 DB’s and 66.8 DB’s at 1200 rpm.
Here are some other cc’s with single outboards for comparison: If you compare all these cc outboard boats at the same rpm / speed level to the Yamaha, the Yamaha is only slightly louder In most cases. If a person was riding on the cc console seat of the Yamaha, the majority of noise is gong to be coming from the wind. Is the Yamaha louder? Yes, ,but not by much.