I have an old 2 cyl 17 hp Arona diesel in my yacht. Its very noisy in the cabin as it thumps away. Is there anyone out there who knows what I can use to insulate the box cheaply and efficently. Or is spending big money on sound proofing the only way. one person suggested cork? will this work or will it rot. The boat is carvel planked. The engine box is ply wood.