I have a set of EMI Thunder aluminum exhaust manifolds and SS risers with the extra 3" height on my 383. It's 9.8:1. I wouldn't call it exotic but it has a somewhat aggressive cam, by no means radical. 218/224 @ .050 and .565/.57 lift with 109 LSA. (ed. 113 lsa, 109 icl)

It's freakin loud inside the boat, to the point of requiring sound reduction.

I know most want the loud, but it requires shouting to communicate. So I'm thinking of ways to keep as much power as possible while mitigating the decibels some.

I have the Formula Silent Thunder baffled platform.

Thoughts,
Dyna mat? Is there any sound absorbent that's better in a marine environment? Is it OK to use, any drawbacks?
A rubber gasket along the leading edge or all the edges of the engine cover/sunpad?
Exhaust Baffles?
Less cam?
Way less cam and wimpier risers?
Way, way less cam and factory exhaust?

Quit crying and drive faster to get ahead of the sound? It IS way faster.

Maybe just try turn downs to direct the sound somewhere else? That would be my first try...

I have same comp cam, but 113LSA, in a 350, with same Eddie exhaust. In fact,boat on the same lake as you. I would get pulled over alot for exhaust noise (even with stock motor) before installing the old style (corkscrew) GGB inserts. Never got pulled over for noise after that, even with the engine mods.

Can't help with the Silent Thunder box, but figured I'd relay my experience on the lake. I would quiet it down a little, even though they don't seem to be as tough now as they where not too many years ago.

Also, being too loud out here doesn't do the rest of us any favors. Non performance boaters equate loud exhaust with being too fast.

Edit in: sounds like you are having fun with your new motor. Congrats !

It should be pretty quiet through the Silent Thunder. Have you modded the platform in any way? Even with the baffles knocked out it should be manageable.

The Silent Thunder box USUALLY has "dams" that hold water in it for the exhaust to gurgle thru. Pretty effective. But if you have knocked out the "dams" or drilled relief holes large enough to let too much water out, then there is zero baffling. Also, when using aftermarket exhaust, some of them have "reduced water" thru the tailpipes. If that's the case, then make certain that your water "dumps" still dump INTO the Silent Thunder platform or.. no baffling. Additionally, if the dams ARE in place, and you are dumping ALL engine water INTO the platform (into both sides), then you can install expanding rubber (wingnut) plugs into any relief holes in the platform to "tune" your baffling water.

A lot of guys knock out the dams FIRST THING.. Unless you purchased the boat new, be sure to double check that.
There should be a dam that holds water about 3" deep, and then farther towards the exhaust should be a "top down" divider that forces the exhaust to go under it thru the water and then out over the "dam".

SB I might have called it 109 lsa when that's the intake centerline. I ripped off your cam idea from a post way back somewhere.
And it's not too loud outside the boat according to my brother who video'd it for a couple a moments.
I still haven't passed by a patrol under power though.
I got a chance to run it wide open the other day, reached 5000 on a 21 stainless pretty effortlessly before I let off. It felt like that was near the top though. I don't think it would turn a 23. I was giggling like a schoolgirl.

Is the box loose or rattley? If so that can cause quite a bit of noise inside the boat. Both my boats with silent thunder with baffles taken out were pretty quiet in the boat, but the exhaust was also further away from the helm since the boats were longer. My 206 has no platform on it, and it's way louder in the boat, too loud to talk at more than an idle.

I have not had the platform off, it's not loose or rattley. It takes a bit to drain when I take it out of the water so the baffles are hopefully in there.

Is it the exhaust noise or the engine noise that's the problem?

Great question. The engine itself should not be noisey.

Cool !

Mine (5.7/350) turned the boat's favorite 21" to 6200 (ooops) last summer with only about 12% slip I think it worked out too. Short blasts too. LOL.
My 23's didn't knock down the rpm enough....so I am trying to figure out what to do as most 25's jump up in diameter, which this boat does not like.

Glad your having fun.