Ive use Kilmat on our last 2 boats, makes a pretty good difference. The first boat I put it on the trans cover, fuel tank cover, and on the bottoms of the locker storages. (wouldnt recommend putting it on the bottoms of the storage tubs again)This boat Ive only put it on the trans cover as the majority of the sound seems to come from it. One other area on the Makai, the trans tunnel cover doesnt seal up against the wall/firewall/engine divider very well. There is roughly a 3/8"-1/2" gap there. Adding a rubber piece of weather stripping D seal there makes a huge difference as well and still allows it to flex if need be.