2022 Sound Proofing

[JimLevin]

Update, for anyone interested, got the back wall of the gas tank soundproofed with my 3 layer/3 step process i used. Added foam on the trans cover, the trans cover gap AND underneath where the floor panel covers the gas tank at the very back end, along with what I did to the engine storage bay. Also did some of the sides of the hull around/near the v-drive. Also added rubber butyl and 1 thin layer of foam to the first engine separator panels nearest the firewall/backseats and to the bottom side of all horizontal fiberglass areas over the engine in the engine bay.

WOW, what a difference. Gotta say, I am calling it a complete success. As quiet as the new Makai's we test drove or quieter. Even my wife was said, "I think you need to start a business soundproofing boats, I can't hear the engine or whiny noise anymore!"

No more whine on acceleration and a lot less engine noise overall. Can barely hear it idling, the exhaust bubbles are lounder than the engine. Roughly, not counting wind noise, about 8 to 10db? lower, according to my apple watch sound meter. Before and after. Hard to describe but no whine at all, no high pitch wind out of the v-drive now. (2019 Makai w/400 engine)

NOTE: left the boat cover at home, did not stuff it under the rear movable seat as @Hayden suggested, so the above is without the boat cover helping. Suppose that would do even better. Spent, maybe, $150 or so for everything. I used some spray glue to attach the acoustic foam in places where the stickiness just wasn't enough. The sound can now not get past the back side of the gas tank, as I foamed all those areas off, left small bottom areas open for water to drain back. My goal was to sort of 'seal off' the engine and trans drive area from the rest of the boat with the foam and butyl rubber to contain all that noise.