We have a Perkins 4-108, but I suspect the noise level is quite similar. Rainshadow, hull #126, has good sound proofing already attached to the sole floor, so we’ve gone after trying to improve other areas.
We’ve noticed a lot of the rattle noise is coming from the throttle control area. I stuff a towel between the cockpit side and the control housing, and it helps me be less irritated. Not a long term solution, but helps with the frustration too little wind to sail.
Also, we get a lot of prop noises coming from the aft cabin, so we always shut the aft cabin doors when motoring.
We replaced the engine mounts a few years ago, and that seemed to reduce the vibrations and therefore the noises from rattling throughout the cabin.
We need to replace the foam strips that outline the sole floor doors, as they are compressed badly. Depending on where we stand, there can be very annoying rattles and sound transfer.
Marilyn