Pink Panels might not work very well
Sound insulation in boats is a fairly complex subject...If you will go to www.soundown.com and read on that site, you will find out a lot of information that will make you realize you will get some, but not much help from the rigid foam panels...also, I would worry about flame retardant characteristics of some types of plastic foam panels.. basically, good sound insulation comes from having an engineered composite material (to absorb the sound waves and convert them to motion (heat) to absorb the sound) and sealing as many holes and ways for the sound waves to get out of the engine enclosure. This gets tricky as you still have to let air get into and out of the engine compartment...baffles usually do this, but again, it is not a totally simple subject. go to the soundown website and read the soundown 101 material and you will have a better idea of how to accomplish what you are trying to do.