Mr Wizzard wrote:
So I got this cheap(er) 2005 Bayliner 175 Capi,
and I noticed that the Merc 3.0L/A-1 is louder
than other, and older Bayliners. I also notice
that some of the older Capi's w/ the 3.0L/A-1
has this foil-backed fiberglass insulation that is
taped to the inside of the engine cover. So I
got to thinking, can I insulate the inside of my
engine cover, and other surrounding surfaces
in, and around the engine compartment to help
deaden the engine sound? This 175 also doesn't
have a padded seat on top of the engine cover,
so there is really nothing to absort/deaden the
sound. Not a big worry, just wondering...

Thanks


Install some thin sheets of lead-based sound attenuation material.

Here is a popular brand:

http://www.acoustiblok.com/marine.html