[sawdustdad]

I have 6CTAs on my 3700. Engine noise at the helm is not that loud, but the high pitched whine from the turbo is the most noticeable sound. I think gaskets and sound insulation under the bridgedeck would help you. I have 2 inch sounddown insulation under my deck.

I also have the factory helm A/C that pulls air from the cabin, and lots of sound gets transmitted from the engine room through that duct. (the blower is in the ER). Since I don't use that any more (have installed A/C units under the seats) I plan to close that hole off, but there will still be some noise transmitted up both sides of the bridge area as those areas are open to the engine room below. Speakers mounted in the bridge deck sides provide another path for noise to the bridge. Back enclosures might help there. I guess my point is that there are multiple ways for ER noise to make it to the bridge.