Hi Jim, I love this stuff...it is really a heat shield, but likely helps with noise as well. My engine is in the middle of the boat, so I don't quite have the noise issues when all the 'holes' in the cabinetry are closed. I tend to keep them open though, because I
want to hear any changes in the old girl's temperment.
heat shield at Amazon.com
I'd also recommend checking out magazines like Good Old Boat...they have advertisers that have some engine box insulation solutions also.